The reason for Bishop's visit was said to be because she was "with a business executive team with interests in PNG".
"Yesterday in Port Moresby I was very pleased to catch up with my good friend Hon Julie Bishop, former Foreign Minister of Australia," Pato wrote on his Facebook page where the picture appeared.
"I had a lunch meeting with Julie Bishop to discuss a number of issues with her during her private visit to PNG with a business executive team with interests in PNG."
Bishop is a household name in PNG going back to 2014 and earlier.
On her first visit to Papua New Guinea as Foreign Minister, Bishop reconfirmed the high priority the Australia-Papua New Guinea relationship has for Australian foreign policy and declared her deep affection for the country, devpolicy.org noted.
"A frequent visitor to PNG as shadow minister, Bishop was a familiar face to Papua New Guinea government ministers, business and media on the first day of her visit in Port Moresby.
"Her decision to visit PNG three times for extended trips while in opposition was smart. She appeared instantly at ease in her press conference with Minister Rimbink Pato at Parliament House in Port Moresby and has been treated as an old friend rather than a new kid on the block," devpolicy.org noted.
She also regularly campaigned on behalf of women in PNG.