Change of address question

I moved to another apartment in the same town recently, and changed the address online for both AR11 and I485. However, I did not received the confirmation letter from USCIS. So I went to the local office. The officer there told me the address was not changed. Although this officer said she will send a letter for me to request the address change, I still have a little bit concern whether I missed some letters during this period. Why USCIS cannot do this kind of simple things right! Furthermore, as you know, the USCIS won't let the post office to transfer their mail the the recipiant's new address. The undelivered letter will be returned. Then I called the 1800- number. The person told me that they should have records online of the returned letters. Does it mean we can see the online status change? Any one has experience like this? or any comments? Thanks.