B737-300 CREW WAS INFORMED THE ACFT THAT THEY HAD FLOWN HAD LIGHTNING STRIKE DAMAGE THAT WAS DISCOVERED BY MAINT.

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LIGHTNING STRIKE DAMAGE ON ACFT. I WAS INFORMED BY A GND OPS AGENT IN ZZZ1 THAT THE ACFT WE HAD TERMINATED ON THE EVENING BEFORE WAS DISCOVERED TO HAVE HAD A SIGNIFICANT LIGHTNING STRIKE; RESULTING IN SIGNIFICANT DAMAGE TO VARIOUS AREAS ALONG THE TOP OF THE FUSELAGE. AT NO TIME DURING OUR FLTS DID WE ENCOUNTER ANY LIGHTNING; OR ANY CONVECTIVE WX WHATSOEVER. THE ONLY CLOUDS WE HAD WERE SOME THIN LOW STRATUS TYPES AROUND MHT. WE OBSERVED NO AVIONICS PROBS; ELECTRICAL PROBS; OR ANY OTHER ANOMALIES. DUE TO THE LOCATION OF THE STRIKE DAMAGE ALONG THE TOP OF THE ACFT FUSELAGE; IT WOULD HAVE BEEN EXTREMELY HARD TO HAVE SEEN ON A WALKAROUND; EVEN IN BROAD DAYLIGHT IN ZZZ WHERE WE TOOK OVER THE ACFT. MY BEST GUESS IS THAT THE DAMAGE MAY HAVE BEEN DONE 1 OR MORE DAYS PRIOR TO OUR FLTS. I FEEL THAT THE FO DID A VERY THOROUGH WALKAROUND IN ZZZ. I ALSO FEEL THAT MAINT PERSONNEL WOULD LIKELY BE THE ONLY ONES THAT WOULD HAVE CAUGHT IT; WHICH WAS THE CASE. I REALLY DON'T KNOW WHAT WE; AS A FLC; COULD HAVE DONE DIFFERENTLY TO HAVE CAUGHT THE DAMAGE.