Updated- end of thread,something in the black tank.

Go to amazon and buy one of these cheap endoscope that will plug into your phone or tablet. It also has a little hook on the end for capturing it and you can see where it is on your phone screen.

Link

Same thing happened to me a few years ago, although I lost just the sprayer head and back plastic piece on the very end. That was the last time I used one of those sprayers. I got the piece out, but yours will be tougher because it's bigger. The way I got it out was, with an empty tank, strategic tapping on the bottom of the tank to coax it over to the tank outlet. Having the RV tilted a little could help. Once it was at the tank outlet I unfortunately don't remember how I got it the rest of the way out. It might have been by filling then dumping the tank, while tapping on the bottom to coax the piece over the ridge at the outlet.

magnet won't work, grabber tool wont work and also can't bend. Find a long flexible stick in the yard and put some really good double sided tape on it and stick it down there to retrieve it. This is with the tank emptied of course

I would fill the tank and see if it comes out the drain. Next attempt would be with a metal coat-hanger with a nice hook on the end. Maybe a couple tries including a few fill and drain cycles with RV tilted pretty good toward the exit. Last resort would be to rent a plumbers camera to see where it was and again hook it with the coat-hanger.

Best of luck.

Magnet? Go on eBay search MAGNETS and choose a 20 x 50 mm Neodybium grade N52 Nothing with a lesser number. 316 stainless is horribly expensive. If that ring is Chinese even 18-8 grade would be a dream. Try 12-5 -therefore magnetic. If it isn't chrome plated pot metal.

The only solution that I can offer that has not been mention is that you need to make something like this out of a heavy gauge wire.

Take a piece of wire and wrap it several turns around a broom handle or something about the size of the object you are trying to retrieve. On the other end make a crank handle. Insert it down the toilet and and do a gentle twist as it goes down. You should be able to feel it if it grabs hold. Then gentle pull it out.

I have use this method to retrieve wire from electrical conduit.

Ugly job!

But it needs to come out. Not good leaving it.

I would try to fish it out, either from the toilet on top (remove the toilet itself first), or from the waste valve side. Your specific plumbing will determine which is more practical. You could try renting a sewer vision system, so you can see into the tank. Then use a wire with a hook to snag it and drag it out. Maybe use the bore scope from one end while fishing from the other.

I bought one of the pick up tools previously linked at Lowe's for use in a boat gas tank ( long story ). It worked great but I think the one I have is only 24 inches. You may need the 36 inch one or more. Also the gripper does not open very much which could be a problem. Maybe try a plumbers snake with a wire or coat hanger on the end for a hook.good luck

Tanks are all enclosed. It would be best if we get it out the toilet route.

Well the next problem of not getting it out is jamming the valve open,it needs to come out as it will eventually clog and collect debris.If you can't hook it can you get at the tank?Can you get at the tank to move it around with a heavy magnet against the bottom to help align it?