OK, just checked The Miz's
Twitter feed...here's what I can piece together. The Miz made an appearance at a toy store in London as part of a promotion in which a lucky kid won a "supermarket sweep" of the store. "Supermarket sweep" was just the term the store used, and this promotion had nothing to do with the television show by that name...at least, until the wrestling news websites jumped to conclusions.
Maybe I'm wrong, but that's the way I interpreted the whole thing. I'm almost hoping I'm wrong - I'd like to see Supermarket Sweep come back to TV.
I thought Chris Jericho was a capable host on Downfall also, incidentally.