Is my money on Betfair and OnGame safe? Im unsure!!

I withdraw some money off a table $279.  However the money never went into my account.  Only by accident I noticed (I play 1000 hands and day and take money from tables many times a day) this money had not gone back into my account.  After contacting betfair, they deposited only $199.  After another complaint and nearly 48 Hours later they deposited the balance.

I’m concerned because I only noticed this by mistake and I’m worried has this happened before and I have not noticed?  The reply from betfair states they do checks every 24 hours for any money locked in.  However their first check didn’t find all of my money.  Also I am unsure if to believe betfair. 
Has any of you had this problem before, and am I right to be worried?