This happened to a friend of mine too. she had put a top in a black trash sack and set it by the door to pick up on her way out. Her husband mistakenly thought it was the final trash to put out before the truck came and lovingly took it out just as the truck arrived. 10 minutes later my friend went to pick up the bag---Ouch it was in the trash and picked up.
After that I bought the clear bags to use for quilt transportation, then when I put a quilt in I write in Large black letters QUILT DO NOT TRASH. So far its working.
sure hope your bag turns up.