It seems that the highlight on a preset in the Preset Collection is lost if you click and release on the Tool Settings palette title bar (without changing anything on this palette). I think I've also seen the preset selection go away under other circumstances, but I can't seem to recall exactly when. I would think that the selection for a particular tool preset should only disappear if a settings change is made to that tool and not under any other circumstance.
Also, after just starting AR3, when selecting a tool and with the presets palette open, none of the tools show a selection highlight in the presets. Shouldn't there always be a preset selected when you switch to a new tool if settings haven't been changed?
This is just a minor annoyance in an otherwise great program.