I submitted my tax returns, however, I completely forgot to add a w2 file. Will the IRS automatically incorporate this into my file? Will I still get a refund, and will I owe or receive more?

Like many others, COVID-19 led to my unemployment. I received about 15k in benefits (before tax was withheld). Prior to this, I was working at a restaurant for about 2 months. At this restaurant, I made about $1300.

I didn't receive the w2 (from the restaurant) until after I had submitted my return. I completely forgot about it. After doing some research, it seems like I will have to wait until my e-file is rejected or accepted. If it is accepted I understand I will likely have to mail in a 1040x (unless the IRS fixes it for me??). 

So, if it is accepted:

Will I receive the refund?

Will the IRS automatically add the small amount of $1300 in income to my file?

How will they notify me about its absence? (mail? TurboTax?)

More importantly:

Would this additional income hinder my refund or increase it? 

I'm super annoyed with myself for forgetting this w2. I'm in desperate need of money, so I am hoping that the return will be accepted (and I receive my refund).