Was it just the alarm or any form of symptom too? How long were you on your graph in the 3.4 range for? (Approx.)
In my experience with a low. It can stay there on the Libre for 40 minutes event though I personally feel better & my meter agrees?
There can be a lag due to a theory I have about interstitial fluid being the least priority (the brain being the first.) with a low recovery? (Just a theory, my brain & eyes waves the “white flag” first.)
I do feel you need to get some indate strips if only just to back up your Libre the next time it happens?
If I genuinely go low. I always mark “the meter says.” Where the graph suggests otherwise. Or I could wind up labelled “hypo unaware.” Which I’m not. Though, my alarm & Libre does give me an advanced 10minute warning that lowers the impact of the hypos, for me..