Does a divorce take place if you swore by it that you would pay the bill, then discovered that your money was not enough, so your friend paid on your behalf, and you then repaid him the money later?

It appears that your colleague's payment of the amount does not constitute a breach of the oath, and therefore your wife has not been divorced. The reason for this is that the intent of the swearer was to bear the actual cost, and this is referred to as "Bisat al-Yamin (definition)" (the carpet of the oath) by the Malikis and "Muhayyij al-Yamin" (the instigator of the oath) by the Hanbalis. Both consider the reason for the oath and prioritize it over the literal meaning of the words. Therefore, there is no breach on your part as long as your colleague paid on the understanding that you would reimburse him, and you have indeed reimbursed him. It is important to be mindful not to endanger the marital bond for trivial reasons.