LSD is the one drug where if your test kit shows you have the actual substance, then contamination isn't really an issue. There are only a handful of drugs that are active in the dose levels that fit on a square of blotter paper, and if the blotter has actual LSD on it then the chances of someone bulking it out with something else are basically zero.

Basically the risk of getting 25x-NBOMe or DOx instead of LSD is very high, but the risk of getting NBOMe mixed with LSD is negligible.