why did half of my registrations disapear?

I just checked this morning and previously had 1015 registrations and now i have 500 ish. Can you advise why? 

It looks like your account was over limit for stored submissions at some point.  When that happens, submissions in excess of the most recent 500 are hidden.  Since your account is Bronze, they should have been restored but it looks like they were not.

I restored the hidden submissions and they are now available once again.