This is almost certainly Railway's log pipeline on their end, not your setup.

The giveaway is that it dropped in two places at once: the Railway dashboard and Locomotive/BetterStack. Those are independent consumers, and the only thing they share is Railway's log delivery. A BetterStack or Locomotive config problem wouldn't blank your dashboard, and a dashboard glitch wouldn't stop logs reaching BetterStack. When both go dark together, it's the source feeding them. The 2-day window with no deploy on your side fits that too, and Railway has had ongoing infra/migration instability lately.

To confirm in a minute: hit your service so you know it's actively logging, then check if anything shows in the dashboard. If the dashboard is also empty, it's not your BetterStack pipeline, it's upstream. At that point the move is to file with Railway with your service ID and the rough timestamp things stopped, and check the status page for anything log related. Not much to fix on your end if it's the pipeline, but the timestamps help them trace it.