No excuses but the kid might have been having an off day. It happens.
I had a similar experiences in a music shop in Liverpool. I wanted a bass, tried it, wanted to buy it and the chap just acted like he could not be arsed helping me out with either a box or bag to put it in - replied in mono-syllables and shrugs. Decided to buy the same bass on line. Didn't put me off the shop though as I know they have some good staff in there too. About a year later I wanted to buy an Ibby - turns out the same lad was on duty. This time though it was night and day; he couldn't have been more helpful.