Dear Larian Studios,
I know you put a lot of effort into this game and the patches.
Nevertheless, Hanal Lechet not only disappeared for some people, it's new stats absolutely won't make sense. Why would you give a two-handed weapon a +1 on single-handed?
Please fix that. ASAP, gotta redo the fight against Murga, since that is bugged, too (I can't fight for the Champion title with my Coop mate, Arran just says something like: "hah I thought you had the guts to fight for the champion title "as if I didn't want to fight!

I think I've figured out why, due to a mod that passed on that bug, and unfortunately it was actually the attempt to make it Two handed that caused it to disappear, and thus Larian reverted the change back to single handed again.
See this pic
Hanal Lecget Helmet?

It is set as a Two Handed Axe, but becomes a helmet, for unknown reasons.
That can't be equipped as a weapon, and is why already equipped ones disappear.
Maybe this new info, will give Larian a clue, as to why this simple stat change, had such unexpected results.

Meanwhile read the changelog, and use the email support link if you want it restored.
I expect you'll need to send Larian a savegame, and they will edit that manually.

Changelog for patch 3.0.150.954 (added 31 October 2017):

- Hi everyone,
- Unfortunately, we introduced new issues with our big patch from last week. Thanks to feedback via our support channel and forums, we were able to track down and fix the following problems:
- When the host or client had the Elemental Affinity talent, and the host was standing in a surface, the client's skillbars would be empty after loading a savegame
After updating the stats of the Hanal Lechet Axe, some players reported it disappearing completely, instead of returning to the inventory as intended. This was due to an error in updating stats on off-hand slot weapons. This is now fixed, but unfortunately, this does not return the axe automatically.
- If you have continued your journey through Rivellon without the axe and would like it restored, please contact our support team at supportdos2@larian.com.

See this thread on the Larian Forums, for more details.
Hanal Lechet (WPN_RC_UNIQUE_Axe) | Divinity - Original Sin 2 - Technical Problems | Larian Studios forums

Dafuq, a helmet?
I don't get it atm. Is the axe supposed to be two handed or not? If it is, it does not make sense to give it +1 single handed!

First fixed the missing link at bottom of first post that gives more details.

Original release mistake, was setting it as a single handed axe.
When it was noticed it was patched, with what is a simple text edit,.
That should have worked, as it does for every other simple stat edit.
It's exactly what most mods do.

Hanall Lechrt entry had this one line edit (Third line in Entry)
new entry "WPN_RC_UNIQUE_Axe"
type "Weapon"
using "_RC_TwoHandedAxes"

Single handed axes use, the next line instead, and this is what was patched.
using "_Axes"

That's when the problem you have was created.
It makes no sense, to anybody why it changed, and all the original reports were of it disappearing.
So Larian reverted the patch, but that didn't bring it back, and nobody understood why, it disappeared to begin with.

Then I discovered the Helmet bug, which explains both why it disappeared, and failed to return.
The game totally removed it, as a fatal error, because it couldn't no longer exist as a weapon.

Now I've reported it's changed to helmet, maybe Larian can find the underlying bug.
Then they can make it Two handed, as originally intended.
Until that time, it' must remain the one handed weapon, to even exist as a weapon.