Jigsaw Puzzle Worry

Bought a five hundred piece second hand jigsaw puzzle of a paper mill in Wisconsin at the local carboot sale for 50 pence a few weeks ago and it was only when I got round to starting it that it occurred to me that being second hand there might be some pieces missing. Often thoughtful people, once they have had the full enjoyment found from completing the puzzle themselves and with an eye to passing said puzzle on for others to enjoy as much as they themselves had at some point, can either donate it to a charity shop or, as is the case here, by selling it cheaply at a carboot or jumble sale, will be inclined by said thoughtfulness to put all the puzzle pieces into a suitably sized see through bag (possibly a sandwich bag or a freezer bag, something of that ilk) that they will then secure with an elastic band and then place that  into its box thereby keeping all the pieces together safely. Sometimes they will put a small sticker on the front of the box on which they have written "Complete" to reassure the purchaser that their jigsaw experience will not be marred by the frustration of missing piece or pieces. My jigsaw had none of these reassurances but I decided to go ahead with it anyway because I had already found all the edge pieces and put them in place before this worrying thought of missing pieces had occurred to me and I considered that I should continue with my endeavour whilst putting my worry to one side. Fortunately my concerns turned out to be unfounded and all the pieces were present and accounted for and the puzzle was satisfactorily completed without any problem. Whew.