Well op I don't think you are the only victim here. I have once had this experience before on sporty bet, where my one of my lost ticket disappear from my bet history I searched and I didn't see that particular one. I was angry though but because the game was Lost, I didn't bother to check anymore, because it was pointless searching for a lost game. I believe that if the game was won it couldn't disappear just like that. If I did not had such expirience I would have agued with you but I guess I have also expirenced it.
Well... It is good to hear someone else has also had an exact experience because I am just speechless trying to explain things out about the strange act with this site and it is becomed difficult for the house to believe me with the fact that I can not proof this due to the fact I don't have evidence of my claim.
Since you havent placed a bet and lost money, does it really bothers you so much? I think here is what has happened, you have selected game outcome, clicked on bet, but odds have changed and you had to reconfirm your choice. But, since you were distracted or havent paid much attention to it, you have made a click on a page somewhere and updated/refreshed it.
Non of the above was faulted because after I have placed (confirmed) the bet, thereafter, there were still other games I played which then when I accesses those other games on the "settled" and "unsettled" bets history before the 29th and 30th when the Barcelona and Arsenal matches were played, the lost history bet was still there in my "unsettled" bet history since it was a future bet of which confirms I played the game.
While I won't be on panic to this strange experience, I will take it likely but still, I will get to the end of it and will update the house.