What does it mean if someone says brb and comes back but doesn't speak?

[Anonymous]

What does it mean if someone says brb in a convo (online). They come back, but don't start the convo. Wait for a while, and then go offline?

[Anonymous]

Something else came up. Or maybe they just didn't feel like talking anymore. I have to be in the right kind of mood to talk online.

[whist]

Maybe they're just too busy to resume chatting. Don't think too much about it?

[Brandan_Cromartie]

It means they saw a ghost.