Thanks for the offer Tim, but I didn't see it in time. I took a 5 month holiday from Gomix/Glitch instead.
I had a similar lost content event today, but nowhere near as serious, only losing 2 lines this time. It's related to network connectivity. The safe thing to to do is to completely stop any kind of typing when there is "Reconnecting..." message at top right, except to copy everything from the current window to somewhere else for safe keeping.
I get the reconnecting message several times an hour, sometimes several times in a few minutes. Other browser windows do not show a connection problem, but their behaviour is quite different. Almost all passive consumption (reading, searching, etc.). My suspicion is that my upload link is too slow or has high latency.