Managed to do the post ride space out and left my Garmin Edge 500 on my bumper yesterday afternoon. Was parked in the first lot of McDowell Mt park. Must have fallen off between the bathrooms and the exit because there's no way it could have hung on long. Went back this morning and no sign of it nor at lost/found.

Posting here on the rare and lucky chance one of the MTBR crew found it.