For sometime, I have been sending for first day cancellations to be applied to covers that I have serviced myself (i.e. with stamps bought at my local post office on the date of issue, applying them to my own envelopes and mailing them with a return address label to the first day of issue city.)
This has worked out fine in most cases. In fact, I have a pile of serviced FDC's on my desk that were recently received for the Jazz, Go Green and George Washington issues. All were postmarked and returned in a cellophane wrapper and cardboard backing with the return imprint on the cellephone "if undeliverable, return to SFS, Kansas City, MO."
Fast forward to today and I just received a pile of the first day cancels I had requested for the Alan Shepard/Messenger Space Issue. None of them were returned in cellophane and as a result, after I removed my return address label, they are all defaced with bar codes at the bottom and other postal markings on the back that the cellophane was supposed to protect against:

Am I doing something wrong? Is there a standard as to when the USPS does or doesn't use the cellophane wrapper when returning first day covers?
I'm confused. Had I known that the covers would be returned without the cellophane wrapper, I would have mailed them in differently, so as to avoid the undesired postal markings, but there was no reason to believe they would be handled any differently than any of the other FDC's I processed earlier in the year.
Could it have something to do with the Kennedy Space Center cancel that is not processed through SFS in Kansas City, or is this just a streak of bad luck? I suppose I could return the covers and complain that they didn't service them right, but it's probably not worth the hassle.
Has anyone else experienced this problem with the Shepard/Messenger issue?