First of all - thanks for emailing the author of these changesets. It's not the first time that this particular user has made questionable edits like this. I'm sure that all edits were made in good faith - just that sometimes, they don't seem always particularly based in reality.

In order to get the old "detour" data back, you've got a few options:

1) If the changes had been recent, and the whole changeset is rubbish, then a complete changeset revert using JOSM's reverter plugin would have been an option. As Simon says, normally 6-7 months is way too late for that - other people will have edited many of the ways since. In Qatar that may or may not be a problem - I'm not sure how much regular local mapping is going on.

2) Another JOSM option is the "undelete" plugin. That requires that you find the numbers of the ways that have been deleted (and from looking at this changeset I'd guess that this way is one of them).

3) If you're not a regular JOSM user, then Potlatch 1's "undelete" option might be the easiest to use (I'll assume that this way is indeed the one to restore):

From the history page for the way, open a deleted node page in another browser tab and select "view history".

That will show (in the previous version) the location that it was deleted from. Click that, and you'll be taken to that location in the map.

Select "edit with Potlatch 2". Edit the browser URL so that instead of something like

http://www.openstreetmap.org/edit?editor=potlatch2#map=18/25.36404/51.44839

you get

http://www.openstreetmap.org/edit?editor=potlatch#map=18/25.36404/51.44839

(i.e. remove the "2" after "potlatch")

From the "Advanced" menu at the bottom select "Undelete" and wait a few seconds. You might get an error message, but ignore that - what you should see is some new bright red ways. Click on each of those in turn until you find the number (in this example 256138077) that you are looking for. Click "click to unlock" on the way and then immediately save.

Then edit the area in the normal way again using your normal editor - you'll see the undeleted way is back again, but you'll need to check it to make sure that it joins everything that it should.

4) One other option (mentioned only for completeness) is the perl revert scripts - but I wouldn't suggest trying that unless you've done it before.

Whatever method you end up using, it might be a good idea to ask in the #osm IRC channel (either for someone to help with the undelete, or to double-check what you've done)