When you leave the arena, did you get the weapons that you had before you entered the M4 arena?
Probably not...
Also DM servers have no "ammo" constraint coz it always give 9999 ammo.
So the DM scripts hardly care if you ran out of ammo or you still got the wep.
Though if RPG scripts didnt care about ammo...you can easily abuse them, buy 1 bullet and fire it 9999 times.
Locking a weapon is easy.
It doesnt actually lock your weapons...
First it disarms you completely, then it gives you a M4...
So you have only fist and M4.
Ofcourse the same happens in Argo when we have the LMS event.
Also it happens on /c restock for cops and /c gear for SWAT.