My freezer gets a big block of ice at the bottom about once a year and this time when I went to fix it I found that some form of putty/sealant/insulation had fallen and clogged the drain.

Can anyone help me determine what it is so I can replace it (if need be) and what purpose it serves (to satisfy my curiosity)?

It's a thin clear strip of plastic film with a firm but pliable gray putty on one side that's about the consistency of stiff gum.

Here are some photos of the unknown objects. I'm sorry the putty one looks gross but that's how I found it.

Thanks.
https://image.ibb.co/eLGuZc/20180322_235838.jpg
https://image.ibb.co/deB6fH/20180323_000637.jpg