AT ABOUT 0250 EST, CONTROL TOWER PSNL AT THE GRAND RAPIDS ARPT HEARD A 'MAYDAY' CALL FROM N23TC, BUT WHEN THEY TRIED TO COMMUNICATE WITH THE ACFT, THERE WAS NO RESPONSE. THE CALL WAS REPEATED SVRL TIMES. A CHECK AT THE LOCAL ARPT REVEALED THERE WAS AN ACFT MISSING. A SEARCH WAS INITIATED, BUT THE ACFT WAS NOT FND UNTIL THE FOLLOWING EVENING. IT HAD CRASHED WHILE IN A STEEP NOSE DOWN, SHALLOW LEFT BANK ATTITUDE. PIECES OF WRECKAGE WERE FND UP TO 300 FT FROM WHERE THE ACFT IMPACTED THE GROUND. NO PREIMPACT PART FAILURE/MALFUNCTION WAS FND. HOWEVER, THE NON-INSTRUMENT RATED PLT WAS FLYING IN ADVERSE WX WITH LOW CEILINGS & VISIBILITY. ABOUT 25 MI SSE AT GRAND RAPIDS, MI, THE 0251 EST WAS WAS, IN PART: 300 FT OVERCAST & 1.5 MI VISIBILITY WITH FOG. PRIOR TO THE FLT, THE PLT HAD BEEN CELEBRATING IN A SALOON. TOXICOLOGY CHECKS OF HIS LUNG TISSUE FLUID & BILE SHOWED ALCOHOL LVLS OF 0.104% & 0.128%, RESPECTIVELY.