sports book made a mistake, or have they? need advise

so 5 days ago i made 2 deposits to a major sportsbook , one for 400 one for 500 . they always debit it from my bank same day.5 days went by and nothing. my bank says theres no pending withdrawls.

my question is have they made a mistake ? i still have 900 in my sports book acoount. if my withdrawl option by check goes through and i cancel my debit card will it be their loss? are they going to come after me for that $ or they legally cant persue action since im in the us. ??

thanks for your inputs preciate it