THE ACFT WAS RPRTD MISSING AFTER IT DEPARTED SAN JOSE, CA, AT ABOUT 1852 PDT ON 6/9/87. A SEARCH WAS INITIATED, BUT THE PLANE WAS NOT FOUND UNTIL THE WRECKAGE WAS DISCOVERED BY A HIKER ON 6/30/90. THE ACDNT OCCURRED NEAR KEARSARGE PASS AT AN ELEV OF 12,000 FT. WX AT THE ACDNT SITE WAS NOT KNOWN, BUT ABOUT 173 MI WEST AT SAN JOSE, THE 1846 PDT WX WAS IN PART: CLEAR, WIND FROM 290 DEG AT 14 KTS. THE PLT TOOK THE ACFT TWO DAYS AFTER HE HAD AN ARGUMENT WITH A GIRL FRIEND; HOWEVER, THE OPERATOR STATED THAT HE 'HAD PERMISSION TO FLY THE AIRCRAFT AT HIS DISCRETION AFTER (BUSINESS) HOURS.' PIECES OF WRECKAGE WERE LOCATED NEAR THE BASE OF A CLIFF. A DIAGRAM PROVIDED BY THE INYO COUNTY SHERIFF'S DEPT INDCD THE ENG CAME TO REST SOME 200 YDS EAST OF THE MAIN WRECKAGE. THERE WAS EVIDENCE THAT THE ENG WAS PROVIDING POWER TO THE PROP, WHEN THE ACDNT OCCURRED.