Certain UI elements carry over from the hideout into the match.

[Twisted Egg]

When starting a match certain pings and the kill feed can persist into the match and never go away.
All of the times I had it happen to me I was in a party.

in this screenshot you can see the ping for ivy being visible despite her not being in match.
I unfortunately don't have any images of the kill feed staying but it has happened to me a couple of times.