This situation has happened to me several times:
When walking in the double grass with my first two Pokemon of similar level to the area (Pinwheel Forest, for example)...
...my first two Pokemon get KO'd at the same time in same turn (Razor Leaf, from Sewaddle/Swadloon)...
...basically, when that happened, I was either UNABLE to bring in a replacement Pokemon to battle for ANY of the sides let alone BOTH.
There a way to bring a pokemon into that bad situation or am I to just power off, power on, and continue from last save point?