AF for a few hours then gone?

So AF was scheduled for Thursday. Before going to bed on Wednesday, I saw brownish spotting in my panties and thought it was the start of AF. I used a pad and went to sleep. Well, in the morning I saw only light spotting on the pad. I showered and started the day. I didn’t see any spotting the whole day and I guess AF has stopped or something. After peeing and wiping, I can see very light brownish stains, but nothing in the pad. I don’t have menstruation symptoms as strong as usual.

What does that mean? Normally, I’m pretty regular with my menstruations and I’ve never experienced something like that. Please, does anyone knows what’s happening with my AF?

I don’t think it’s implantation bleeding since they usually occure a few days after ovulation...