If you've taken another substance before, and get sold it later on under the guise of something else, you may be able to recognise. You can also recognise "This isn't LSD", having taken plenty of LSD before. However, if you're asking "How can I tell exactly which drug I took?" - you really can't unless you've tried that particular chemical before and recognise it, psychedelics are all so similar that just by describing certain unique effects of each one wouldn't be enough for you to differentiate and say "Ah that blotter I ate was definitely 25C-NBOMe" just from someone's suggestions/description.
The only real way to tell would be to send off anything in question to a lab for testing.
If this deteriorates into "How can I tell
which drug I took?" then this'll be closed as we don't allow substance ID discussion here, but as a "Will I know if I was sold something other than LSD?" topic I think this is cool to remain open for now