I think messages need to show sent time and received time. I had basically the opposite issue recently:

1:23 Coworker: Hello

1:24 Me: Hello

[20 minutes elapse]

1:44 Me: Did you need something?

[No notifications until leave for the day]

[Checks back hours later and the conversation appears as]

1:23 Coworker: Hello

1:24 Me: Hello

1:25 Coworker: Could you herp the derp?

1:30 Coworker: Nm got Mo to herp the derp.

1:44 Me: Did you need something?

1:45 Coworker: Nah I'm good.