Yes it is totally normal to feel down about losing a job, seasonal or otherwise.

As for the cell phone use, at my job it's just a given that you don't use them during work for non-work related things like adding others on snapchat. I carry mine around in my pocket as a watch, and it also counts my steps, but that is it. I use it during break times and lunch only.

Even if there were 12 other people using their cell phone at the same time, it is still likely against the rules at your workplace and you need to take responsibility for breaking that rule. It'll help you with future jobs to not point fingers and take the responsibility yourself.

In your next job, I would advise you not to use your cell phone during work hours if there is a rule against it. It does affect how the employer sees you, and how long you keep the job for. I wish you all the best in your job search.