pms

Hey guys I have had a pm dissapear from my inbox.. I know 100% I have not touched it or deleted it, but I go into it tonight to use the details in it and its just gone. details are from a customer... and I am a little concerned this has just dissapeared without trace. How can this...

hi guys i am nearing my limit of pm's but i dont have the tickbox in my pm list to tick and delete them? going to hit the limit shortly what do i need to do? thanks