Not so sure that I would pull out the BS meter just yet .............. I am so anal that I would have found a way to test it that night.
I actually have 2 test kits for ethanol content sitting in the barn .................. maybe a buddy of his had a test kit laying around and they used it ?
I could be wrong though ..................
FIRST thing I do when a saw comes in "not running right", is dump fuel into something to have a looksee, while the owner is present, regardless of time of day...