I think it's important to understand why your nurse practitioner felt you should discontinue the med. If you don't know why you stopped the medication, then you probably shouldn't take it again until you clarify the discontinuation reason. For example, if she felt that Seroquel made you suicidal or manic, then you don't want to be taking it.

So long story short, no, I would not take a PRN I'm no longer prescribed if I didn't know the reason behind the discontinuation.

In my non-professional opinion, I think you should wait until your nurse practitioner gets back in the office, or if you cannot wait, ask the office if you can speak to another doctor or nurse practitioner. I'm fairly certain your nurse practitioner has notes that she takes down during or after every session, and so another doctor or nurse practitioner could read those notes for you.