the K-1 is reporting the profit and loss of the enterprise.
If you invested $20k and the business is now liquidated, sounds like you have a capital loss of $20k that is reportable on Schedule D. Do you have documented evidence that the business is worthless to prove that the sales price is zero against a cost basis of $20k?
Edit: since you state the business is sold, that is the evidence required to indicate your selling price
