Embarrassing Question...
The most likely answer is your mind is playing trick with yourself. You didn’t really have 19 gold before.
Other wise, you might be hacked, and strangely the person hacking only took 6 gold(very unlikely). And Anet will notefy you if anyone logged in your account with a different IP through mail. I dont’ think that’s likely.
Maybe it was a 4 instead of a 9?
In any event, something similar happened to me recently.
I could have sworn I had like 17G, but then had less than 12G. I had bought a few things on the TP.
I decided it seemed entirely possible I had remembered the number from before I bought a few materials on the TP. I didn’t see anything unusual in my TP purchases. None of my other stuff was out of the ordinary.
In the end, I remembered that 5G is about $1 and decided it wasn’t worth stressing over.
Maybe you placed a buy order on the tp and the item you bid for hasn’t arrived yet? You should check your tp history.
When you bid on the TP, you put the money up in advance (automatically). It’s held by the TP until you cancel the order or you buy the item. It’s possible this is what happened.
Maybe you accidentally bought a 5g sharpening stone station recipe from a merchant after the event.
also when you sell you pay the costs for putting it up on ah. I Always thought that taking items off again would refond the full amount but it doesnt refund kitten. Yesterday i lost 40-50g that way by putting things up for sale and taking it off again to undercut another person and back up again. Suddenly i noticed i was down 40-50g. That really sucked