Same. On XBOX EU. My partner got the talisman and a box. I got just gold.

Editing to say I finally got it by doing the quest on a character that had not done the 1st Thieves Guild quest.

I repeated the quest on a different character and got the talisman. The major difference was that I escaped in time and didn't choose a emotion response when talking to Quen to turn in the quest.

There is someone on the upper level of the main room. That can give you the talisman if you lost it. I am pretty sure if you have this achievement progressed to this point. You can talk to them and get the talisman.

Something is buggy with this mythic for sure. I got one and put it in my bank. Then later, I ended up with another one somehow that was stolen and I had to launder it. Then I couldn't put the second one I laundered in my bank for some reason, so I just destroyed it.

Not sure what's going on here, but seems there are at least a couple things happening regarding this mythic that shouldn't be happening.

This one seems to be a bit buggy. The Talisman isn't actually added to your Collections until you talk to the Talisman Expert. No idea why since everyone else is "why don't you just keep it?", strongly implying that it's already in your inventory (it isn't), but that's what put it into my Collections. The other weird bit is that asking the Expert about the Talisman produces a dialogue line to the effect of "here's another, but keep better track of your stuff in the future," which also makes little to no sense.

To follow up on @madman65's comment, not picking it up is very likely not the problem. It's quest-markered (and quest-journaled) as one of the two items you must pick up. Quen will not speak to you and advance the mission to the "let's get out of here" phase until both the Codex and Talisman are in your inventory and the exit door is not interactable until after speaking to Quen. Short version is that you can't leave the strongroom until you have both items.

I'd need to go back through again and look for the exact point where it happens, but the Codex is on the table in the Den when you enter to turn in the mission; you don't even get the option of turning it over to anyone or dialogue indicating that it has already happened. Basil's dialogue says that you have the Talisman in inventory since you hand it off to him and then he tells you that he's giving it back.

Whenever the Codex gets removed from inventory is probably the point at which the Talisman is removed, too. Note that I skipped through Quen's dialogue in the strongroom, so that might be the point of handoff. Still got several characters who haven't started Codex Caper, so I'll keep an eye out for it.

EDIT: Yep, you hand off the Codex and the letter about the bank safeboxes to Quen during your dialogue with her in the strongroom. The Talisman is still in inventory after that conversation, though. The Talisman, however, disappears from inventory about the time you enter the Outlaws Refuge after exiting the estate. Had it and the extra loot when I talked to Skeever Neevo, but all of it was gone when I got done fencing the loot I picked up at the estate. Nope. I was still in fence dialogue at that point; all the loot and Talisman were still in inventory before speaking to Basil, but the Talisman was gone after speaking with Basil.

EDIT: Ooooo! Interestinger and interestinger. If you snag all three bonus items on the way out of the Yvierry mansion, then the Talisman is added to your inventory along with that Curated Baraha's Curse coffer. So the short version seems to be that if you grab fewer than three of the bonus loot items, then the Talisman disappears after talking to Basil and you can retrieve it from the Talisman Expert after talking to Quen to complete the mission (the Expert is not up there before talking to Quen, but watch carefully and you can see her poof into existence). If you retrieve all three, then the Talisman goes back into your inventory after completing the mission and no need to talk to the Expert until later.