I'm wondering how "open" the thief is being on social media about the circumstances allegedly triggering the mental health downward spiral, because "I am suffering a mental health downward spiral" is going to net them a lot of sympathy and support, while "I stole Friend's prescription medication and replaced it with a similar-looking OTC generic version of a different medication" is probably not going to get the hugs and positive vibes the thief is receiving.

There is no need to resume contact with this person, and if anyone asks you why, tell them, so that they do not become victims also.