And before you say its because they replace them, thats not what I mean! 
Basically I added Pyro mines to my char only to find to my great disappointment that not only do they get rid of standard mines they appear to only let me deploy 1 !!!
So I thought nevermind I will reset my char back to level 20 re-buy my original abilities.
I have just done that and now even though I have mines and extra mines as abilities I cannot, repeat cannot select them as an ability in game. I just get a blank space where they should be in game.
sigh