So after 4 days of rest, chill and party with old friends, travel on to daughter and son-in-law.

You did a wonderful tour.
It's not so easy with the tandem.Don't get angry about the flooded track. Since you still have the route covered in your head, you can put the track together again afterwards.
There are suitable "tools" from Garmin.
But also goes directly in Komoot, if not so perfectly.
Just reschedule the missing piece (set the appropriate pace using "fitness") ... then you export the route to any directory on your computer and import the file as the route you have traveled into Komoot again.
Now you can also add pictures and write comments about them.
You have to live with small inaccuracies in the basic data (possibly wrong date). (You could only do that with Garmin track editing.Because most cell phones are not waterproof and the display is difficult to read when the sun is shining, a navigation device (XP 7 waterproof) would be a sensible investment for a frequent cyclist like you.