I was playing today as Necrolyte... So, I had my power treads, then bought perserverance and wards. I put the wards on courier when my power treads disappeared from my inventory.
I didn't lose the stats bonus and movement speed and I can use all the slots...

Screens:

http://cloud.steampowered.com/ugc/64...66002D8373D12/
http://cloud.steampowered.com/ugc/64...1BE8595A30911/

Pt's disappeared about 14:13

Match ID: 1528069