Originally Posted by NeedHelp

Sent on 8-15-12 using USPS express.
Package was delivered on 8-16-12 signed by J.Lo
Receipt was sent to me on 8-21-12 6:47am
Checked my case status at uscis.gov and it says "your case can not be found at this time...."
last four digit of the receipt number is 31xx.