Keeping an Eye Out for Anna

Day 3, 0400 UTC. Niue to Tonga, Position 18 33.371s;, 173 34.339w
On Saturday night when we were enjoying a jolly good time at the Niue Yacht Club, an un-Godly storm blew through from the east.
The local constabulary came by and we heard that an EPIRB had been activated so he was calling out an Orion from New Zealand to search for a yacht in distress between Niue and Tonga. The much awaited supply ship was diverted to join in the search. After a while we braved the elements to get back in our dinghy to return to Bristol Rose. It was an uncomfortable night but we were confident that the excellent moorings maintained by the Niue Yacht Club would hold.
On Monday morning the 2 crew members of Anna arrived on the supply ship with only the clothes they were wearing. Their 57ft catamaran had flipped over when the wind suddenly blew up from 18 knots to over 60. It only took an instant. One crew member ended up in the water and managed to get into the dinghy. The other acted on his first instinct to get to the EPIRB quickly to activate it. He remained inside the upturned catamaran until they were rescued, about 18 hours later.
We were at the Yacht Club when they came ashore. They were full of praise for their rescuers and spoke about how well the crew looked after them. They were very lucky sailors. Anna's position when they were rescued was 19 degrees 32.305s, 172 degrees 14.60w.
Since we left Niue on Monday we've been on the look out for the upturned cat. It won't be easy to see in daylight and impossible to see at night. The last thing we want to do is hit it. Trying to calculate it's position as it drifts is difficult. The owner expects it to slowly drift in a northerly direction and is hoping to salvage the vessel.
We have the Kingdom of Tonga in our sights and are about 20 miles from our waypoint on the east coast of Vava'u. Bristol Rose is just drifting along comfortably at 3.3 knots speed over ground with spinnaker flying and 7 knots of wind out of the east (a far cry from the conditions of Saturday night). We will take the spinnaker down when night falls and may then have to motor the remaining miles. We'll arrive in darkness but should be able to navigate to safe anchorage.