IRC I think is more intended for live discussion in the moment. It connects you to chat rooms, and is not suitable as a persistent messaging app.

IRC is for chatting. Need help? Hop on and see who’s around. If no one answers, come back later

Ask if they are open to move to something else /s

I use irssi. When you start it up, if you run:

/lastlog -hilight

It will list the log of messages you received while you were logged out.

Get yourself an ssh account somewhere, maybe here : https://sdf.org/ or here https://tildeverse.org/ and use screen or tmux to keep your IRC client session alive, so you can scroll back to older messages. Make sure to adjust the screen scroll back buffer if needed : https://www.baeldung.com/linux/scrollback-buffer-screen-session