Samilar situation

I sent my application on 9/28 to Texas, and the checked had been cased on 10/4. But I only got 485 receipt on 10/11. Today I received a notice said "undelerable mail returned" for the 140 receipt. I am afraid you probably have the similar situdation. On the back of your check, you can find your case #, starting with EAC, WAC, LIN, or SRC (my case # is SRC). Then you can check the staus online. Does it make sense?