I bought one of the cash cards from the xbox store which gave me about $1.25m in-game cash for roughly £13.50 directly from my linked bank account card. Then I went and purchased the most expensive property in the game, which was $400k from the money I just bought from the store. I used the property whilst I played for a couple of hours before saving the game twice (just to make sure it did) leaving the game and switching off my xbox. A few hours afterwards, I went back online to find that the property was gone and appearing as if it was never purchased, but the $400k wasn't there either! So basically, money from my bank has gone towards downloading some in-game cash that has partially disappeared. I've sent rockstar a message but there isn't any sign of a reply. I feel like I've been robbed - it's frustrating. Any form (info/advice/updates/etc) of help would be appreciated!
Online is pretty buggy right now, it's entirely possible that what you experienced is one of these bugs. http://www.computerandvideogames.com/431870/rockstar-working-around-the-clock-to-resolve-gta-v-online-problems-errors-and-bugs/