Rp Glitch???

Dear Riot, Recently, i bought Dragonbalde Riven with 3,850 rp (something around that) and it said when i was about to buy that i would have 2,500 (about) rp left. When I bought the skin though, I had 1189 RP left. Can someone explain and can i get my 1,300 K rp back???

Edit: When I press buy (on something I can, but don't buy it) the game says i have 2.5k rp. Could you fix this visual bug???