I got a letter on Feb 15th saying in about 7 days I'll get my EIP2 for $600 but never got it, There was no info on the IRS Get My Payment tool. How do it get it?1040-X?

you must file a tax return and put the amount you did not get on 1040 line  30.

That's the only way.

I already did my tax return. so should I redo it and where will I find the 1040 form ? cause I checked and I can just do the 1040-x efile on the 25th update of turbotax on that update they said they will add the 1040-x so I can just do that specific one.

That is all you need to do is follow the instructions for the amendment (Form 1040X).  It is scheduled to be available tomorrow.  This year, amendments can be e-filed, so the original and changes can be e-filed with TurboTax.   When you prepare the amendment, you will go directly to the stimulus questions and enter the amounts you received for the 1st and 2nd payments.   When you enter 0 for the second one, the recovery rebate will be calculated and added to Form 1040X.    I will leave the instructions here, but as mentioned by you and above, it won't be ready until at least tomorrow.   

You will need to amend if you already mailed your return (or the government accepted your e-file) and:

• You forgot to report income or claim dependents, deductions, or credits (such as the recovery rebate).

If IRS records show a check was issued to you, they will reject your amendment.

You might have to do a "lost check search" before you can get that $600.