code: func (b *batchSpendReporter) NotifyUnspentAndUnfound() {
  	log.Debugf("Finished batch, %d unspent outpoints", len(b.requests))
  
  	for outpoint, requests := range b.requests {
  		// A nil SpendReport indicates the output was not found.
  		tx, ok := b.initialTxns[outpoint]
  		if !ok {
  			log.Warnf("Unknown initial txn for getuxo request %v",
  				outpoint)
  		}
  
  		b.notifyRequests(&outpoint, requests, tx, nil)
  	}
  }
docs: // NotifyUnspentAndUnfound iterates through any requests for which no spends
  // were detected. If we were able to find the initial output, this will be
  // delivered signaling that no spend was detected. If the original output could
  // not be found, a nil spend report is returned.