On one request, I texted around 2 p.m., asking for an appointment at something like 8 p.m. the next evening; on another request, after a few back-and-forth texts, the therapist said "yes, I'll schedule you" -- and never replied to any follow-up texts; and on a third one, I agreed to re-schedule an appointment at the masseur's request (he asked to re-schedule and suggested the alternate evening, and it worked for me) -- and he never replied. These were all masseurs I had seen multiple times over multiple years.
I thought about a phone glitch as well and considered sending a second text -- but now I'm not available for at least a couple of weeks. The masseur is highly recommended by someone on this site.