First Special Mission From Sidorovich

[arottweiler]

I took the first special mission from Sidorovich at the start of the game and can't remember what it was but I've just delivered the X18 documents to Barkeep and when I return to Sid and ask for a special mission he says I've not completed the last one. I have three active missions which are

Find docs in X16

Find Strelok

Find out what happened to Ghost

Why is Sid still saying the special mission hasn't been completed even though I've delivered the X18 documents to Barkeep?

I've only failed two missions which are

Get out of Dark Valley

Help The Stalkers

[Xottab_DUTY]

Probably, this is because you've failed "Get out of Dark Valley" mission.
You was supposed to escape from Dark Valley to the Cordon using the path in the southern part of the Dark Valley and after that Sidorovich was supposed to call you to his bunker to give you a new mission.