Peach........as to the train trip from Vienna to Zurich......
The main line splits at Innsbruck. To the right (north) it the route to Munich. Straight ahead (west) is the route through the Tyrol and Black Forrest to Frankfurt. At Lauterach, Austria, it splits again....to the left the trains cross the Rhein at St. Margrethen, Switzerland and head back south to Sargans on the Swiss side of the Rhein and then on to Zurich.
If teams did take the overnight EN (EuroCity Night) train or the RJ (Railjet) train, they could exit the train at Buchs SG station in Buchs, Switzerland and either walk, drive or ride across the bridge over the Rhein to enter Liechtenstein. There are no trains to Liechtenstein. The bridge at Buchs seems to be the main entry to Liechtenstein. There are only about 6-7 bridges. To me, they could have done tasks in both Liechtenstein and in the Buchs/Sargans area. It is only about 10-11 miles from Buchs to Sargans.
After finishing in Liechtenstein/Buchs/Sargans, I would assume that one of the Swiss Regional or Interregional trains would have been better to get back to or onward to Zurich. They are more numerous than waiting for the long distance trains.
The spoiler got on the IR 1776 at Ziegelbruecke, Switzerland, which is about 1/3 the way from Sargans to Zurich.
As apskip pointed out.....it is easier to fly to Zurich from Vienna, then take the train from Zurich to Buchs SG. Unless Production did another rolling pit stop and used the train from Vienna to Buchs SG. One thing I have noticed in TAR 18, is what I call a "rally point." By that, I mean that park/courtyard in Sydney where all the teams hung out for a while and the same thing in Lijiang......where those people talked to Christina. Production may have been doing this all along and I just never noticed it till now. If they did have a pit stop around Liechtenstein, Buchs or Sargans.......K/J could have been in transit to another "rally point" in Zurich or to their hotel in Zurich before the next leg. Or as speculated before, they are eliminated and on the way to a hotel/flight to Brasil. I would think that Production would want to separate the teams on the way to Zurich to keep them from all being noticed......maybe.
Someone mentioned what a small country Liechtenstein is.......yes it is one of those small European pincipalities.......but I just think of Liechtenstein as a very large bank.