there is a couple ways to get around this. One, line the pan with foil before making up the baking item or pouring a reheated later item in. Then when frozen, just lift it out and store some other way- in a bag etc. then when time to eat- just place right back in the pan and bake etc.
or when at a rummage, resale good will whatever- buy pans there. I bought a 9 x 13 pan with a cover for a dime at a white elephant sale. I use it all the time to bring to pot lucks, a dinner to someone etc. It always gets back to me no matter what. I bought it thinking I would not get it back- no. If I paid top dollar for it- I would never see it again