The boat was recovered last Saturday off Indonesia, the IMB confirmed to United Press International. A naval aircraft later found the tug's barge, carrying heavy machinery and construction materials, floating in the heavily used sea lanes.
The IMB said the boat was en route from Malaysia to the island of Borneo when shipping authorities lost contact with the vessel.
Indonesian authorities issued no information on the event but the IMB warned ship owners of the dangers of piracy in all seas.
Last week another reported attempt in Indonesian territorial waters was logged with the IMB's Piracy Reporting Center in Kuala Lumpur, Malaysia.
A duty officer on a bulk carrier anchored off Samarinda on the southeast coast of Borneo noticed an intruder on board and sounded a general alarm. The intruder fled in a waiting boat along with two other suspected pirates, a report on the IMB Web site said.
Piracy rose to record levels last year, with Somali pirates behind 56 percent of the 352 attacks reported up to October when the IMB issued its annual global piracy report.
"Figures for piracy and armed robbery at sea in the past nine months are higher than we've ever recorded in the same period of any past year," IMB Director Pottengal Mukundan said.
Somali pirates are intensifying operations not just off their own coastline but further afield in the Red Sea -- particularly during the monsoon season in the wider Indian Ocean, noted the IMB, whose piracy center has been monitoring piracy since 1991.
"With unprecedented boldness, this August pirates also boarded and hijacked a chemical tanker at anchor in an Omani port, under the protection of coast state security."
Somali pirates were involved in 199 attacks in the first nine months of last year, up from 126 in the first nine months of 2010. But Somali pirates hijacked fewer vessels last year, taking 24 ships compared to 35 for 2010. Also, hijackings were successful in 12 percent of all attempts up to October 2011, down from 28 percent in 2010.
The IMB praised the work of Bangladeshi authorities in helping to reduce attacks in their territorial waters.
Indonesia remains an area of concern.
"Robbers are normally armed with guns, knives and or machetes," the report said. "Many attacks may have gone unreported. Pirates and robbers normally attack vessel during the night."
Also, attacks in the Straits of Singapore are increasing.
Senate Democrats to pull all-nighter on climate change
Interpol investigating stolen passports on missing flight