pretty much the same thing happened to me when i went to petco a while back to get a rat for my bp i had at the time. i asked if a certain medium rat they had would be too big for my bp, i told her how big my snake was and whatnot, and she replied with "you dont want to feed it anything bigger than its head or else it will choke" LMAO so i bought it anyway and was just the right size! i cant stand how dumb the employees are there (at my store at least) i feel so bad for their reptiles, they are probably barely feeding the snakes anything if they are following that kind of advise, plus its the only petstore in my town, any other one is like an hour away...been trying to get a job there tho