I cannot find any mention of what to do when my ranch is depleted. I still have a gang reserve but my "ranch hands" (all 3 of them) are dead.

What action(s) do I take now ? (Can't "Hit the Town" or "Head Back to the Ranch")

Thanks in advance !

On page 10 of the rules, one of the three game end conditions is "Any player has no cowboys alive". Therefore, in your case you would not be able to take any further actions since the game has ended.