Are items that disappear from Fallout: New Vegas companion inventories lost forever?

Twice now, I've completed a side quest in Fallout: New Vegas, received a unique weapon, given that weapon to one of my companions and then had the weapon disappear completely from the game. Is there a way to get these weapons back? I'm playing the 360 version, so console shenanigans won't work.

I have a theory about why this is happening, but I haven't been able to prove it. I'm guessing the weapon condition drops to zero while the companion is using it. When my own items break down in use, they just get grayed-out in the Pip-Boy screen, but they can still be repaired or transferred to a container. Maybe the companion inventories can't handle such unusable items?

I think this may be a bug. I have Veronica and gave her the Q-35. She was doing fine until I saw her shooting her stock 10mm at a giant radscorpion. I look in her inventory, no Q-35. I use a console code to give myself another one, and give it back to her (items are created with full CND). She did not equip nor drop it, I checked her inventory again and... no Q-35.

I loaded from before I gave it back to her, generated another one and put it in her inventory, saw it sitting there before I closed it, transferred it back to me and her a couple times, and now it seems like it's staying there. For now, anyway.

This is definitely sounding like a bug though, unless I'm missing something.

The poster who made the comment about the patch deletion only working on the PC was wrong, fortunately for those of us on the XBox 360 (and hopefully for you PS3 users as well). The solution for me ended up being very simple but I will list step by step directions to clear any confusion.

(NOTE: If you rely on your auto-save or your auto-save is your most recent save you would like to play from, I recommend saving a new manual file before attempting the steps below.)

1. Exit to the XBox dashboard.
2. Go to the "My XBox" menu and scroll all the way to the right and select "System Settings".
3. Select "Memory".
4. Choose the appropriate Storage Device, likely your "Hard Drive".
5. Select "Games".
6. Find "Fallout: New Vegas" and select it.
7. Find the file labeled "Fallout New Vegas Title Update #5 (the number on yours could be higher if you are reading this after another update, or lower if you somehow have an old update) and DELETE it (do NOT move it, as the game will still detect it).
8. Launch Fallout New Vegas as you normally would. A guide window will immediately open once the game launches and will ask if you want to apply the available update for the game. IMPORTANT: Choose "Cancel".
9. Load your desired save file (I believe you may need to load one from outside the casino or other place that confiscate your weapons).
10. Upon loading, you may need to exchange some items with your companions to balance weight as some item weights were different before the patch. Make sure your companions have the room they will need to hold all the weapons you had them carrying beforehand.
11. Fast travel to the location where your weapons were lost and save a new file at the door (just a precautionary measure that should always be taken when doing this sort of thing).
12. Enter the building and allow the guard to take all your weapons.
13. Exit the building. Your companions should now have all the weapons they had before they were stolen the first time.
14. Save a new file.
15. Exit to dashboard.
16. Start the game back up again.
17. This time, allow the patch to be applied.
18. Load your newly saved game as normal, but this time, be careful to dismiss companions or take all their weapons and only let them hold your non-weapons (although this could possibly allow the other similar bug to occur where Companion "Unique" weapons disappear) before entering buildings like the casinos.

If the problem occurs again, you should be able to repeat the steps above to resolve it again, however, prevention is the best medicine.

Can't help but clarify. It is a bug. Sometimes weapons get knocked out of their hands and disappear. Had it happen while fighting deathclaws. The chainsaw dropped out of Veronicas hands and rolled down a hill and I just turned my back and it was nowhere to be found.