I would expect that they would have some type of evidence of a cover-up, they would find receipts of products or have CCTV of him buying cleaning items or even disposal of the cleaning items, they even check mops, buckets and drains for any type of evidence.
IMO if C M was murdered and/or had her remains prepared for disposal at Wildenstein, surely the venue, as a wedding and big events destination has its own "cleaners closet" so all the cleaning items and products are stored together.