When I logged back in today, my horadric cube is missing, but I still hve the Horadric Staff fully assembled. Both in Nightmare and Normal it’s missing.
UPDATE:
I just went back to normal a2 and grabbed it again, but yeah, something messed up if just my cube disappears.
Happened to me just now. IIRC I had experienced the “character already in game” bug last night, but I still had the cube in my stash. Kind of a nuisance, really. Wonder if it’s connected to that server bug?
Me too. Happened twice so far
Same thing just happend to me now. I just signed in after maintenance break - everything seems ok, but the cube is gone. 
Being on nightmare right now.
same happened to me, cube missing. What should I do?
went back and found it in halls of dead level 3, for anyone else who experiences this issue
Lost the cube, Terra’s trick worked for me.
Happened to me too. Game was disconnected and when I went back… cube is gone and I am in act 3 and am unable to assemble flail, brain and eye.
Same here - I was already post-Normal and farming cows. Exited a game after hitting L31. Couldn’t enter the next game. When I check my inventory (personal character stash), the cube is missing.
Just had this happen to me too. Was logged in in Hell mode, went to grab a drink and came back to find I’m logged out. Was gone maybe 5 mins. Logged back in and my Cube has disappeared 