This is probably because you settled the credit card batch, and it's impossible to adjust a payment after it having done so. The best solution to this is to perform a payment audit from Aloha Manager. It should show you full card numbers. If not you may be out of luck, and may be no way to recover those tips.
Select the employees or all, select non-cash payments, view the report and write down the cards with missing tips.
You may be able to get the full card number again through EDC. In older versions of Aloha, you can also try editing your EDC.INI file adding the following:
PRINTFULLCARDNUMBER=1
Stop and start POS Processing if you add the above line to see changes.
After you've gathered your credit card numbers to input. In Aloha EDC, perform a manual authorization but do not include a tip. Instead, input the tip in the "amount" field. The customer will see two charges from you, but the total will be with tip. Often times customers don't have a problem with this, but we don't recommend making a habit of it.