Catalytic converter with no catalyst!

I just removed the catalytic converter from my 2007 Prius. I purchased a replacement some time ago and just didn't get around to making the swap. Thankfully I'm still working at least part-time during this CV-19 crisis, but do have more time available so I finally got at it yesterday. The portion I removed (where the catalysts should be) are completely empty! With a flashlight I can see half way through from both ends and there is nothing there! The part appears to be original (or very similar) and it's just an empty pipe! Has anyone else encountered this? I was expecting to see some very gunked up catalysts and instead there is nothing - absolutely nothing!

In general the car runs well and gets good gas mileage. It currently has 310K + miles on it (248K when I bought it in May 2018). It had an O2 error code when I bought it that I just ignored since it seemed to be running well and we don't have emissions testing in the county where I live. Recently I added some BG 44k Platinum to the gas (also BG products to the oil - but I'll write about that separately). The O2 error went away and I got a P0420 Catalyst System Efficiency Below Threshold error instead. Ran 3 pints of CataClean through the gas over a period of several days and while the car runs even better now I still get the PO420 error after 50 miles +/- following a code reset. Given the extra time available to me now I figure I've run out of excuses regarding the catalytic converter replacement.

I haven't completed the repair yet - it's currently raining and I'm doing this work outside, but I will report back once I have some experience with the new catalytic converter (the one that actually has catalysts in it). The point of this post was to express my amazement that the original(?) part was simply an empty pipe and wondered if anyone else has encountered this same issue? My only other thought is that the part was replaced at some point in the past by an unscrupulous repair shop that profited by selling a fake.

I know the recent catalytic converter thefts are no laughing matter and have caused a lot of grief for those affected. I wish the thieves would have taken mine instead of one of yours. I already had the replacement part and the thieves would have been very disappointed!