My guess is, you are running a steady-state simulation? If you are, then of course you are missing the particle current positions in your particle track summary. 

If transient: Go to Particle tracks>Reporting>Current position and then you can add or remove variables that you want Fluent to report.

If steady state: Try Particle Tracks>Reporting>Step by step and then write the variables in a file

Either way, import the written file in excel and look at the residence time column first (column 1). May be sort the whole sheet according to decreasing residence time. So you now can see your culprits at the top. Column 2 through 4 should give you the particle positions (if the default order was not changed).