I don't understand the scare quotes, prescription for ADHD medication, typically psychostimulants.

They're sometimes used as scare quotes, but they're not scare quote marks they're just quote marks. If quoting a part of somebody's comment to ask about it you're supposed to use them. (That said, I don't know what they were asking about, but you're probably right that they wanted to know what kind of drug was being talked about, or weren't familiar with that word in a medical context at all.)