I did not receive a 1099 so I do not have one to send with my amended return

Which 1099?  1099-R ?  1099-misc ?

and what was your reason for amending?

I forgot to add income from freelance work

1099 misc

But you said you did not receive it?

No, I didn't receive a 1099 Misc form. I had forgotten to add freelance work on my original return. So i added the income to the amended return. I was told i wouldn't receive a 1099 misc form because the work wasn't consistent. So I needed to know what to do if I didn't receive the 1099 Misc form to include with my amended return.

Just keep good records of that income in case of an audit.

Then there is no additional form to send to the IRS with the 1040X.

Even if you had a 1099Misc you don't send it in with either the original 1040 or amended 1040X.