S-Bahn line S3 doesn't exist - Munich

There is S1, S2, S4, S5, S7 and S8, but what about S3?

A moderator ate it.

It's sharing part of the tracks with S8 and S4.

Maybe it says something here about the history: Munich S-Bahn - Wikipedia

Dos is right, its now part of the S8Line- previously the S8 only went to Pasing, and the S3 from the West only to Ostbahnhof. Now they are the same.

Erm no; the S8 used to go to Maisach. Now it goes to Geltendorf after they changed the numbers.

Use the search function. This has already been covered at length before. See Munich S-Bahn History and U-Bahn Trivia For Details.

The S3 was put back into service between Dec04-Dec05 running on the line Nannhofen - Ebersberg . It then disappeared again with the
renumbering of the network in Dec05. Todays S4 currently runs where the previous S3 used to run.

FYI: The network will be renumbered yet again in Nov/Dec 06 to allow for the newer stations and further expansion of the 10min takt routes.
Perhaps the S3 might be brought back yet again, only time will tell..

30.09.1973: S3 München Ostbahnhof - Ismaning opened.

28.05.1988: S3 Maisach - Nannhofen extented.

17.05.1992:
Extension Ismaning - Airport Munich. Replace of S3 between Munich Eaststation - Ismaning - Airport Munich by S8.

29.05.2000:
The lines S3 (Nannhofen - Munich Eaststaion) and S8 (Pasing - Munich - Ismaning - Munich Airport) are now put together again in original state of S3 Nannhofen - Munich - Ismaning (- Munich Airport) befor the route Ismaning - Munich Airport was opened.

This is what is shown muenchen.de as the evolution of S3. It was absorbed as part of S8. It was never part of what today is S4.

You didn't mention the S6: it exists as well.

Forgot the S20 and S27 too

Erm yes actually. When I first arrived in Munich the S3 ran from Nannhofen to the Ostbahnhof, the S8 from Pasing to the airport.

Yes it was. See above. The S4 west of Munich is what used to be the S8 until recently. Your history is not up to date.

They used to be numbered consecutively starting in the north and working anti-clockwise. Now there is little logic in the numbering. Not that there needs to be any.

My friend saw an s3 yesterday at Ostbahnhof - apparently, they are running some random weekends as a nostalgia train, from what my friend could understand. I tried finding something about it online, but failed - does anyone have further information? My friend and I have a running joke about the s3 - if it's really back for a bit, we feel obligated to take the opportunity to ride it.

Sounds like the first ET420 (old Olimpia zug) special trips they usually run. (ET420-001). Did it look like this?
The Sonderfahrplan for the ET420 Has it running around Munich Yesterday June 7th between Ostbahnhof and Ismaning

Was reading one of the S-Takt newsletters and the MVV Wiki. Seems the S3 will be running again in December with the introduction of the new fahrplan.
The S3 line will be brought back to run the Mammendorf - Holzkirchen route. The S8 will now run from Herrsching to the Airport, and the S5 will be killed
off entirely. (S4/S8/S3 Picking up the Old S5 Slack)

Lots of other MVV/MVG changes coming-up in December, so get ready for the chaos..

Big bus changes due if you you travel around the west side Donny Brucker due to the new Bambigarten station.
Also in the north end of town due to new Tram 23.

The MVV really love playing around with the line routings. I don't know any other city that does this. Since they're not actually building new lines, I don't know why they can't just come up with the routings and stick to them.