(Gameplay) Switching Homegurad

I was in a ranked game as malzahar and I bought the enchantment while I was in base, and I couldn't refund it, no big deal. After I backed I then bought the enchantment, and as I walked off the spawning platform I still got the movement speed bonus. I haven't retested this, but I think that it could be that homeguard's time to wear off didn't go away after the item switch. I might have had baron also, I'm not sure.