I amended my return. According to irs website it was accepted, but I think my check was lost. What do I do?

Amended returns don't get accepted since you have to mail it. When the IRS processes it, it gets Adjusted.

It can take them 16 weeks for the IRS to process them.  And they only mail checks for refunds.   After 3 weeks you can track it here,    

https://www.irs.gov/filing/individuals/amended-returns-form-1040-x-/wheres-my-amended-return-1

Did you mail the amended return?  Amended returns are not "accepted" the way that e-filed returns are accepted.

After you print, sign and mail your amended return—1040X— to the IRS wait about 3 weeks and then you can begin checking on it at the IRS website.  Be aware that it can take at least 3-4 months for an amended return to be fully processed (or sometimes even longer.)

https://www.irs.gov/Filing/Individuals/Amended-Returns-(Form-1040-X)/Wheres-My-Amended-Return-1

It takes 3-4 months for the IRS to process an amended return.  When they send a refund, they mail you a check.

Per the IRS amend status website - https://www.irs.gov/filing/wheres-my-amended-return ?

Check for what?  - A refined check or your check to pay additional tax?