Thanks for the save and the step list.
Yes, my guess is confirmed.
I advanced time to 17:00 and took the bus.
I chose Valeries's house as bus destination, and the scene with Alex on the bus was displayed.
I waited and nothing happened.
As soon as I clicked to advance, the message from Tanya popped up and at the same time the watch command on 
mesto variable shown that its value was now 12, which is one of the values in logical "OR" in the "if" clause.
(See attached video - you can see the value of 
mesto being displayed in the top right corner, Console command 
watch mesto)
So, I guess that when we choose a destination for the bus ride (in this case Valerie's house, and for the bus stop near it mesto==12) the number of that location is saved to a temporary variable and the bus scene is displayed, then when we click to advance that variable is assigned to the actual 
mesto mesto variable BEFORE loading the scene.
In this case the assignment 
mesto = 12 is executed BEFORE displaying the scene of the bus stop near Valerie's house.
But as soon as 
mesto is changed to 12 the phone with Tanya's message pops up, and so we 
graphically see it on top of the 
bus scene, but internally the finite state machine developed by Kosmos to track locations already thinks we are at the bus stop near Valerie's house since 
mesto == 12 already.
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Yup, in the second attached video 
BP mesto setting to 12.mp4 i captured VLC window while playing the first video step by step; we clearly see that:
- Firstly the value of 
mesto changes to 12
 
- And only in the next frame the sequence "Tanya wrote something" pops up.
 
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Long story short, when the correct time comes we must already be in one of those places I listed in the .txt file attached to this post, OR be one step from going there by bus, car, or taxi.