My towel bar fell out! No stud, and no space for a big anchor behind the drywall. What now?

Your towel bar fell because drywall alone isn't strong enough. If there's no stud and no room for a toggle, something is likely behind that drywall – a pipe, wiring, or a fireblock. Drilling blindly is a big risk, so use a stud finder with AC detection to scan horizontally. If it's clear of obstructions, a heavy-duty self-drilling drywall anchor might work, but check its weight rating and ensure your drywall isn't too thin. For the most secure, long-term fix without moving the bar, a small wood mounting block spanning two *other* studs and painted to match is a very solid solution. Otherwise, you'll need to pick a new spot or call a pro to safely investigate what's in the wall.