OPINION: we have already found all the probes
It seems that there should be 4 probes for given sector, one trasmitting at :00, another at :15, another at :30 and another at :45.
4 have been found in the rift
4 have been found in the gap
3 have been found in the conflux
this might lead to think that one is missing in the conflux, but:
In the rift and in the gap the given system contined the first probe, then other 3 have been found nearby.
In the conflux in the given system there's nothing: just a single M class (or K, can't remeber). M (or K) main sequence are not bigger than 1000Ls, the probe could be anchored only around the star. Whereevcer direction you enter the system, you should be at 1000Ls from the probe if it was there, since there's not another planet, not even an asterois belt.
So probably the "first" conflux probe went missing (fell in the corona of the starr, kidnapped by thargoids, whatever).
In game they probably never implemented it. They knew we would have found them superfast so they made this trick to make us consume a lot of time in the conflux.
To this I add that a 12 of CMDR (minimum) have searched the sector for 2 evenings. In the other 2 sectors all the probes have been found very fast.
I can be wrong, the probe could be in the outskirts of the area (200Ly radius), but i think we already found all the probes (they can alway ninja patch more anytime).