The recovery rebate credit form never showed up for me

If you have not received one or both of your stimulus checks, you will receive your payment in the form of a Recovery Rebate Credit on line 30 of your 2020 Federal tax return when you file.

TurboTax will compare your one or two stimulus payment amounts to the computations within TurboTax.  The computations within TurboTax are based upon the information that you have entered into the tax software.  If you are due an additional amount, it will be issued as a Recovery Rebate Credit (RRC) on line 30 of the 2020 1040 tax return.

In TurboTax Online, you are prompted to input stimulus check 1 and stimulus check 2 information under Review down the left hand side of the screen.

You can access your stimulus check choices by following these steps: 

• Down the left side of the screen, click on Federal.
• Across the top of the screen, click on Other Tax Situations.
• At the screen Let’s keep going to wrap up.  Click on Let’s keep going.
• At the screen Let’s make sure you got the right stimulus amount, click Continue.
• At the screen Did you get a stimulus payment? you can update your stimulus check entries. 

See also this TurboTax Help.