Lost Private Messages

I woke up today and checked my PM for a JV that I was in contact with someone about and I noticed that the PM was gone. I then checked my sent folder and noticed the guy I was in contact with had gotten banned, and his post count etc. got nulled. I was wondering why PMs from banned members get removed, along with their posts (I don't get why this is being done either)?

if i were you i'd pm a mod asking why that member got banned, that's exactly the case when you'll get answer your question
and after you know the reason, you can decide if you want to work with the banned member furthermore or not
also if you're in JV with somebody, it's a good idea to ask them for at least one alternate way (instant messenger) to contact him/her, because what you do if the forum is down?

why the posts/pms got deleted? the member requested it, or the mods decide to do that in serious cases, which could be a sign for you now to think about the future of your JV