Where have my contacts gone?

As I import my contacts into an excel spreadsheet, we normally had over 3,000. Now my list has been cut to 500. Where have the rest of my contacts gone?

Since your account is currently over limit for stored submissions, submissions in excess of the most recent 500 have been hidden from view.  When your subscription was active, there was no submission storage limit so all your data could be viewed.  

I restored the submissions but they will be hidden once again if the account is not upgraded.  From your usage, it looks like a Storage subscription would suffice.