After a quick skim through the report and voice transcripts, all I can find in terms of direct evidence is a call from the controller to the Tu-154: "...we have traffic at your... 2 o’clock", whereas radar replays show the traffic to have been at 10 o'clock.
If you look at the hard evidence, this radio call is the only indication for the three aircraft situation in the heads of the TU154 crew. But even the BFU investigating the accident assumed, that the TU154 crew was searching for traffic in the wrong sector.