no matter how "tightly" anything is wrapped in paper, tinfoil, or plastic...it is NOT airtight. only things like mason jars and vacuum seals are airtight.
the best storage for LSD (and most chemicals really) is in an airtight container with desiccant, protected from light, in the refrigerator or freezer.
LSD is stable for years when stored in this manner.
however, 4 days at room temperature...exposed to air and light is not likely to have degraded your LSD to a noticeable degree.
your LSD is fine.
blotter squeezed between two objects is not likely to squeeze a significant amount of LSD out of the blotter. i doubt it does so at all.
tabs cannot melt, since they are made of paper. but i suppose the crystalline LSD could melt at some high temperature...something that you want to avoid for reasons of degradation.
do not store your LSD at high temp. and it won't melt or degrade that much.