entry to US after green card

[akgoel]

My father was granted greencard in US in November 2010. He travelled to India on January 4th and returned to US on July 14th 2011. At the time of entry, he forgot to show his green card at immigration. He had a previously stamped valid B2 Visa on his Indian passport that was used by immigration to allow entry into US and a I 94 was issued. Do we need to get this rectified ? If yes how do we do it ? We went back to the airport to request immigration dept to correct it but they refused.