You can also use this tool to confirm an efiled return was accepted:
https://shop.turbotax.intuit.com/efile/efile_status_lookup.jsp
By "IRS can't locate it", are you referring to the "Where's My Refund" tool?
https://www.irs.gov/Refunds
NOTE: When entering your refund amount, use only the Federal refund amount and not any total refund amount that includes a state refund. The figure to use is shown on your 2018 Federal Form 1040, Line 20a.
