If you sold it at a loss, there isn't any depletion recapture. In calculating the loss, however, you would adjust the basis by the amount of depletion claimed.
If the royalty trust is sold at a gain, past depletion deductions which reduced adjusted cost basis must be recaptured as ordinary income. The remaining gain is eligible for capital gains treatment.
From the IRS Part 4. Examining
Process, Chapter 41. Oil and Gas
Industry, Section 1. Oil and Gas Handbook (Cont. 2): For oil and gas property placed in service after 1986, the amount required to be recaptured is the smaller of the aggregate amount deducted as IDC on the property plus the depletion deductions that reduced the basis of the property or the gain realized on the disposition.
Since there wasn't a gain (i.e. gain = 0), there isn't any recapture.
https://www.irs.gov/irm/part4/irm_04-041-001-cont02.html
