Well, based on this new info, it sounds like the phone usage may have been part of the decision.

If I recall, this is a pattern for you with breaking rules that have been clearly explained to you. If you aren't supposed to have phones on the floor then why did you have a phone on the floor? They only keep a few people after the holidays, so it sounds like you sealed your fate by breaking the rules.

And my guess is that your supervisor was nice to you about it so you wouldn't raise a ruckus while she was letting you go.

Many times they smile to your face while shitting in your hand.

Start obeying the rules and these things will stop happening.

Seesaw