Not received receipt of I-485

Dear,

I submitted the I-485 to Vermont Center on 26 September via FeDex. However, I have not received the receipt. I really worry about if my application was received before October 1, 2005, although the proof said that my mail was sent to Saint Albans, VT on 27 September. Does any one have a similar situation? Would you kindly give me some possible reasons? Thank you