When you hit that button, you are not undoing the past. You are creating a new, fragile, blank slate.
They will probably find out eventually, but not via an alert. what happens when you unblock someone on fb
Facebook implements this as a "cooling-off" period. Once you hit unblock, the system prevents you from blocking that same person again for two full days. This is designed to stop on-again, off-again harassment or emotional spiraling. Before you unblock, ask yourself: Am I ready to see this person’s content for at least 48 hours, no matter what they post? Here is where most people get blindsided. When you block someone, Facebook essentially performs a surgery, severing every connection. When you unblock, the platform does not stitch those connections back together. When you hit that button, you are not undoing the past
If someone tagged you in a photo or post before you blocked them, and you unblock them later... nothing happens. That tag is dead. Facebook implements this as a "cooling-off" period