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.