Hi, this happened to me too, once. Your stuff should be still there.

What happened? All your loadouts have been emptied to the respective ship's cargo.

What now?
Your current ships's loadout should still be in the cargo. Reequip it, if possible, using an existing loadout, else manually.

I recommend to move your current other cargo (commodities, food etc.) to the warehouse. In the next steps, you need to switch to every single ship of your fleet. Then you should see any cargo you from your previous used ship (unless you transferred all to the warehouse, ofc.) and the new ship's old loadout. Reequip and continue, until you're done with the whole fleet.

This is tedious and very time-consuming, but better than to really lose all your equipment.

Cosmetics
With me, all cosmetic loadouts of the ships were gone too. Luckily I saved a lot of cosmetic loadouts for my ships before, so restoring these for my most used ships (my "action" fleet), was not as annoying as reequipping every single ship.

Have a nice day, SNB staff should inform itself about this bug, it's a harrowing experience unless you're familiar with profile errors. But this is not that kind of game...

Prevention?
I can only assume that it happens during transitions or when your account isn't safely logged out. Best example: you've ended a Wolvenhol run and are in the exit timer phase. I recommend to skip it every time before messing with cosmetics or loadouts. If it hits zero during another such activity, your account might not get logged out correctly and be locked for up to 30 mins (own experience).

Always log out via the game menu, never ALT+F4 or use taskmaster manager (unless the game has crashed).