Yes, but of course you have to make sure it also stops at Pingyao, or wherever you're boarding!
Damn it! You are right. The Pingyao - Weinan train is sold out but I can buy the Taiyuan South - Weinan. It's a bit more expensive but that's OK.
The question then is, can I collect the actual ticket at any train station in China?
I have another problem. I can't find any train from Luoyang to Xian on May 11th. In China Highlights and www.travelchinaguide.com I see every train with 0 seats left, but in Ctrip I don't see them sold out. It just says "Sorry, no matching results found" for any destination from Luoyang on Friday 11th.
Does anybody know if there's something special on Friday 11th? I've checked other Fridays before and after the 11th and there are trains.
If not, can anybody suggest other option to go from Luoyang to Xian?
Thanks

Well, this is something that happens on China Highlights website. You should try to push "Search" button several times consecutively and the results will appear because there are plenty of trains on the mentioned route.
By the way, it is indeed impossible to buy right now anything between Luoyang and Xian, but don't worry... Just wait until tomorrow and the booking for May 11th will open and you will certainly be able to buy a ticket. One suggestion, it is much better to pay for your ticket more than a month in advance in case that you have exact date of travel. Now, you are right in the middle of "waiting" for May 11th to open for booking at least for China Highlights website.
The problem is that the Chinese booking system goes down every night overnight Chinese time -- I believe the right to 休息 is in the Constitution -- so agencies can't get ticket availability or do bookings then.
I really don't understand how the ticket reservation works :-/
So to sum up. The tickets were supposed to go on sell today at 4PM China time (according to Ctrip)
As I said, it was impossible to buy or reserve the tickets from any site, so finally I reserved tickets from Zhengzhou (the previous station) for the same train on China Highlights
Before paying I've contacted them to make sure it was OK to board the train in Luoyang and they have modified the ticket to make it Luoyang - Xian, so even if a ticket is not available on the site maybe it is available for them to reserve, and they have confirmed that the sell was staring at 4PM, so Ctrip has the dates and the times right.
Exactly at 4PM the tickets were available to reserve in China Highlights, meaning that the number of seats left went from 0 to 99. Exactly at the same time, all the tickets for all trains and all categories from Luoyang to Xian on May 11th went from not available to sold out in Ctrip.
20 minutes later the tickets went from sold out to available in Ctrip. And there's plenty of them.
So now I'm waiting for China Highlights to confirm that my reservation is OK and the ticket is bought.
I'm really puzzled about all this. I just hope the tickets are OK. I don't see why they wouldn't, since there are still plenty of tickets available for the same train on previous dates.
Thanks to all for the tips.