PD
i don't think receipt matters at all.
my receipt from sesa was sent to lawyer first, and my lawyer forwarded the receipt to me, so it's possible the receipt was missing somewhere.
today, when the immigration officer reachs your case, your case is "current" as far as the priority date is concerned, not like several years ago, people would wait for two extra years just for the priority date to get adjudicated. i read an article not long ago. it says that the PD will keep current in the next two years.
my conclusion is, as long as sesa has ever received your file, RD and PD is only for your own reference in the next two or three years.
on my receipt from oh sesa, it specified the receipt date: this is to acknowledge receipt on 1/3/03 of a foreign labor certification application filed by the above employer. this date is the receipt date, not the date you sent to sesa, not the date you receive the sesa receipt.
hope this answers your questions.