I think I dropped the dodecahedron somwhere. I went back to my room and if I remember from the youtube video it was in the same cabinet as all the spells. Its not there. So I went ahead and did experienced the Sensory Stones and told Iannis the Accountant about them. He gave me a wedding ring and a letter. I thought I was going to get a reciept for the Godsmen Foundry but I need the dodecahedron for it? I don't know what to do.

You don't have to have the dodecahedron on you, but you do have to read the entry about the legacy in it to learn its number ("51-AA") to get the Foundry receipt from Iannis; it's a different legacy from Deionarra's, so you have to ask about it separately. If you haven't read that entry and can't access the required information, you can still get your stuff by killing the Foundry clerk, though naturally this should only be done as a last resort, preferably after you've already finished all of the sidequests.

(Of course, entering the Foundry without a receipt is a different problem. The guards will only let you in if you accepted Giltspur's message delivery task.)

Eeek! Yeah, I can't get inside the foundry. I went back to a couple shops to just to check the floors or something. I think I'm truly screwed. I watched some of a Let's Play cuz I thought either I'd figure it out or I'll just see how the story ends, but it just wasn't enjoyable doing that. I think I might just let this game go.

Just to make sure - did you check all of the cabinets? Or did you have the Dodecahedron at some point and then it disappeared? Because there's at least one mod that puts it into a different cabinet than in the vanilla game.

Technically, you can edit your savegame to either add the item back to your inventory or set the variable for the information you get out of it.

I read the dodecahedren about the legacy so shouldn't I be able to have the receipt for the God'sman foundry? 55-AA it says.

To get the legacy, visit the Advocate in Clerk's Ward.