How long will these abandoned bobcat kittens survive waiting for frightened mom to come back?

.....Outside my window. The gardener startled mom away from the lair. She's been gone for 36 hours. It's in an alcove and the entrance is dusted with flour to catch her prints. These two are eyes closed young, noisy, move into sunlight for warmth by day and curl up together at night for warmth. uming an owl doesn't find them, they may be headed to animal rescue if mom doesn't come back by tomorrow daytime.