You can let them log in to their QuickBooks Self-Employed account to verify if it was sent. It can be found in the Documents section. If they're not able to receive any, we're unable to resend it. You'll have to resend the form manually. Here's how:
Click Expenses, then go to the Vendors tab.
Select Prepare 1099s.
Click Continue your 1099s.
Click Next till you're on the Check that the payments add up page.
Select Finish preparing 1099s, then click I'll file myself.
Select 1099, then click Yes, looks good!.
Click Print on 1099 forms.
Click the Print icon, then Print.
Although, if you haven't invited your contractor, you'll have to send the forms manually. You can follow the steps at the top on how to print them, and send them through the mail.