None of the skill bonus items show that the bonus is active in the skills page, but if the combined bonus button (bottom center below equipped items) shows it then it will be added whenever you play a level.

If it shows there but testing in game (which you can do with many skills) proves that the bonus isn't there, then -that- is a bug.

I found that you only get the bonus on Greed skills that you have invested at least 1 point in.

What I have noticed is that for all the items that give a bonus like that, they do not show up anywhere that they are active, no change in the stats on the skills tab, but during a mission I do notice a change for the skills that affect traps, like increased damage as an example, just by equip an item and start a mission build a trap, examine stats, exit, remove item, start same map, build same trap, and compare , yes, old post but new problem I noticed, and had to trouble shoot to figure out.