made an error and don't know how to correct it

one hour ago I mistook seriously and did not realize it. in changeset #41808021 I deleted a line that was the border of a lake, together with the border of a forest. It was (what I did not realize) also the delimiting line of a large area: Danube Delta Biosphere Reserve.
Now that area is broken. I want to restore it as it was, but don’t understand in which relation(s) that line played a role.

The situation before the edit can be seen at
The line started in de right bottom of the map picture connecting to a forrest and ends 18 nodes to the right where it connects again to the same forrest.
Now all the area below that line is now wrong, which is a rather large area of many square kilometers.

Any help welcome.

The changes to the relation can be shown here:

Looking at

It’s clear there’s at least one obvious gap. You can see the changes in each changeset (the ones that aren’t too big) by doing something like:

Maybe you could go through previous changes and see where the missing bits were deleted?

It must have been SomeoneElse (As I had lost direction) to show me the way. Thank you, solved the problem. And learned one IMPORTANT thing in the ID editor: if you don’t see a line, that does not mean it does not exist: it may be hidden by another line through the same nodes. And if you delete, not only the visible part is gone. Had to add a line about 23 km long (the marsh), on top of another (the forrest)

Glad to know that that’s so, I almost was afraid that making changes in the Danube Delta is not for beginners like me. I’m travelling there now and also in the future, I hope, and a good map is precoius also for myself, as an offline copy goes with me on the boat. No Google maps in the heart of the Delta: there is no GSM connection! Details on the map need continous updates, canals block, reopen, etc.