The first thing I tried was using the built-in Xcode crash reports in the Organizer. I assumed that since Xcode has access to the archives and is fetching the crash reports itself, it would be able to locate and use the appropriate dSYMs, but I see unsymbolicated entries for the parts of the stack trace that are in my app.
So that led me to trying to symbolicate manually. I looked up the UUID and then used this, which produced no output:
mdfind "com_apple_xcode_dsyms_uuids == E49A5EB3-C560-3895-B2AE-4CEE263E45CA"
Next I tried looking in the archive for the dSYM itself. I right-clicked on the archive in the Xcode organizer and chose Show in Finder, then used Show Package Contents on the xcarchive. In the dSYMs folder, I see dSYM files for some frameworks the app uses, as well as some of its extensions (intents, widgets) but there isn't a dSYM for the app itself.