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The only way you could be taken off the accounts is if you were a beneficiary and not a joint account holder. In that case, your father had the right to change beneficiaries. This is commonly called a payable on death account. The person has the right to spend all of the money or to change the beneficiary. You are not required to be informed of the change.
If you were joint on the account then the bank should not have removed your name. However, in a joint account one party can withdraw all of the money and do whatever they wish with the money. You should send a demand letter certified to the bank asking why your name was removed from the account and demanding the statements from the time your name was removed.