Return receipt does not have date stamp

I sent off my second DV letter to United Revenue Corp (the first one requested more information so they can find my records). I got the return receipt today, signed by Maria Smith but no "Date of Delivery". Should I go to the post office tomorrow and ask if they have the date it was delivered or should I just use my certified mail receipt that has the date it was sent off and she is SOL for not putting the date on there?

Thanks!