Can i put my retainer in my shirt pocket when i go to the college canteen everyday?

Plastic container: It is always smarter to place a retainer in a plastic case to prevent warpage or distortion resulting in a misfit to the teeth. The container should be ok in your shirt pocket.

Not good idea: Retainers are fragile, easily lost or damaged, and custom made (expensive). They should only be in one of three places. 1) in your mouth, preferably 2) in retainer case, as when eating or playing contact sports. 3). In denture cleaner once a day.