I have created the reverse scenario of this and let me tell you it sucks.
I like to think I'm pretty decent for a hobbyjogger. 2h35m marathon, I've won various local races, etc.
A snotty co-worker was humblebragging about her ex being a triathlete and I asked if he was faster than me. She said "probably" and pulled up some race results. Turns out he'd finished 13th in the pro field at the European champs one year.