The simplest option in this situation:
ask your opponent before your turn — did they check ГО on that road.
Since you saw blue units and the road is empty. If they lied — they violated the fair play rule, refused to answer — contact the judges.
We've been playing for a while — we know that the generator creates such passages.

Here I am running, and I see an empty entrance from the center to the respawn
I write to my opponent "did you break through the passage at such-and-such location?" and wait for an answer/clarifying questions
when the timer is ticking — how much time will that take?

save?
let's say
but abuse like extra scouting is possible here, which can't be verified, but on Jebus it's oh-so-critical
and knowing about this, someone might have too many questions for the opponent...