Presumably a stolen amphora would have been very fancy and possibly conspicuous, so more specifically the joke works like, a person bought a stolen Picasso to h

Presumably a stolen amphora would have been very fancy and possibly conspicuous, so more specifically the joke works like, a person bought a stolen Picasso to hang in his gallery, but crudely painted it over so he wouldn't get caught. I totally missed the pants/pitch joke, good catch. Reminds me of an episode of It's Always Sunny where Frank keeps flushing articles of clothing down the toilet and uses black paint to cover up, except it ends up being a pretext for a later, unrelated bit.