Wow - what good timing.
Now, I am not sure the route they took (I won't know until they get back), but my parents were going from St Petersburg to Tallin last night on their big summer holiday by train to various parts of Europe and Russia.
From what I can make out by the texts I got from my mum, when stopped at the border, their Russian visa had expired by two hours.. leaving them to be detained and held for SEVEN hours to pay some hefty fines (bribes?) and get it sorted.
So by then they missed the train for the rest of the journey and had to find alternative means of transport. The Russians advised they hitchhiked with a Russian lorry driver, a suggestion that was politely refused.