Bug report?

[phenox1707]

Fairly certain this is a bug.

I had a Witchstalker on the board with a Sword of Feast and Famine attached to it, and seven lands on the board. (three forest, two plains, two island). I cast a Prized Elephant, then cast a face down Master of Pearls, using all of my mana. I then accidentally clicked on the Witchstalker, which activated the Sword of Feast and Famine's Equip ability. When it asked me to pay the mana to equip, since I had no mana, I hit cancel. It then proceeded to untap one of my forests and one of my islands. Can't provide screenshots, my computer doesn't do those. I can attempt to provide a screenshot if you'd like, I took one with my phone since my computer doesn't do those all that well.