I hiked desert mountains of the U.S. Southwest with a retired Boston firefighter, whom I met while pedaling a remote Nevada road. The incongruity of his lush New England accent amid those vast arid settings was reminder that we are all travelers, each on our own peculiar journey through time.

Among the surprises of that desert was a proliferation of Mylar balloons, blown from far-away celebrations. (Given the prevailing winds, I suspect most were from the Los Angeles area.) My friend collected those he could reach and packed them out, striving to leave the desert pristine … until he found one from an era long before Mylar, when balloons of thick rubber and twine of jute sufficed.

He estimated it had been there at least 50 years. The dry climate preserves such things well, but there was little left – a glob of blood-brown latex, plus weathered cord bleached near white by decades of intense desert Sun, knotted around a half-buried tatter of paper rolled into a tight cylinder. In it, a child’s prayer in careful Spanish cursive – faintest henna on darkened, brittle parchment – asking God to watch over her mother in heaven. With solemn reverence, the firefighter retied and replaced the note, whispering, “Please, God, let it be so.”

I’ve been traveling the U.S. by bicycle since May of 2016, and for most of the journey, the only camera I’ve used is that in my smartphone. Ah, but use it I have! I’ve taken tens of thousands of photos with it, striving to record, well, everything! And what I cannot capture in images, I describe in the extensive journal notes I compile at the end of each day.

But I do not take photos of scenes, such as of that hand-written prayer, which feel sacrosanct – too precious, too intimate, too private. That’s a personal judgment, not an absolute, but in my heart, reducing a child’s prayer to static digital imagery – a prayer she’d entrusted to the winds – is to cross a line I’d rather not.

Nor can I share a photo that identifies my friend the firefighter. Oh, I have photos of him – lots! – but when I asked permission to share them with others, he declined with respectful eloquence, but for the few I’d taken that did not show his face.

Simplest put, when I take an identifiable photo of someone, it is theirs, not mine. I don’t claim that’s the right rule for every photographer, but it’s the one with which I remain most at ease.

Of what use, then, are photos such as those of him I cannot share? Why take them in the first place? Well, not everything need be published to have value.

I completed my initial journey through the lower-48 U.S. states 21 months after I started. Then I had a second stroke.

The primary impact of the first, in early 2015, was to my vision; I lost about 40 percent of my field of view – that to the lower left. It’s still gone, although I hardly notice now. One doctor compared it to losing a finger to the first knuckle. “The bad news is, it will not grow back. The good news? It will not get any shorter.”

The second stroke impacted my speech, which, unlike a finger, I was able to regain … in part.

I also lost some memory, which I have not recovered … except what I could refresh from copious photos and journal entries and email and text messages and such.

It’s funny how memory works. And how it doesn’t. One of my cousins texted to ask if I had contact information for another cousin, and I recalled that we had a cousin by his name, but could remember no details about him. Nothing. It’s as if I’d found a physical file folder with “Cousin Mike” written on the label tab, but the folder was empty.

I had almost completed first drafts of two books before that second stroke. One, a novel titled Tilda, about a fellow on a bicycle following a talking dog around the country, is a love story. Go figure. I wrote the second, working title The Boy (which purports to be nonfiction), from the perspectives of others I encountered during those first 21 months of bike travel – people like that retired Boston firefighter – sans names, of course, or any other identifiers.

It was when rereading that second book that I realized the extent of my memory loss. I had little recollection of much of it, which, all considered, felt like a blessing. Many of the stories I’d recorded there were (are) as if new to me, in whole or in part. And oh, such wonderful tales! All the more so because the words I composed then now represent their entirety – there remain no other memories to tempt embellishment.

Ditto all those meticulous daily notes of scenes and connections I would have lost but for a longstanding habit of journaling – scenes, such as that of a child’s balloon, and other adventures collected during eight days spent in Nevada mountains with a retired Boston firefighter.

So the photos, even those I cannot share – especially those I cannot share! – are essential to me. They represent the only visual memories I have of many precious connections and scenes, whether or not shareable.

The photo that accompanies this entry did not capture the expat Bostonian in a contrived pose. It’s a position he adopted unconsciously when directing my attention to something I might otherwise miss. I know this, because the notes I completed late that night tell me it’s so, just as those same notes tell me he was pointing to ancient petroglyphs that covered most rock surfaces within sight, including some that left me marveling how anyone, ancient or modern, could survive reaching them long enough to carve such elaborate patterns.

As for the girl, the balloon and the prayer, you’ll have to imagine them, but if I’ve done my job well enough here, you will.