No confidence in shop-am I overreacting?

[Eden]

The right side crank is integrated into the spider that holds the big ring on and the axle (on my Shimano cranks at least). Being all one piece I don't think that it's possible for the right side to pull off the way the left can.

I didn't notice anything amiss before I pulled the crank off - no funny noises, no slipping. I don't think that it simply loosened up though. I think it was installed improperly in the first place... The mechanic that worked on it started saying something about how many bikes had it been on, it was just moved around too much and the bolt holes had stripped.... um no.... that was the original frame it came on and I think it had only been off once maybe twice when I'd had the bottom bracket overhauled... If the bolt holes were stripped well...