To anticipate the travel of a drifting buoy is not an easy thing !. We can look after the currents known in the area where the JOIDES is stationary :

In this part of the Pacific East, in the northern hemisphere, there are three main currents whose position and intensity vary with the seasons:
• the Northern equatorial current, warm, which goes from East to West under the latitude 10° N,
• the Southern equatorial current, warm, in the prolongation of the Humboldt current (cold) who goes also from East to West at the level of Ecuador,
• the Northern Equatorial current, moving from the West to the East, between the two precedents…
 

Then, it is necessary to locate with precision where the JOIDES on this chart is stationed and thus from where the buoy was launched:
The position of the ship was:  LAT: 2.253    LON: -101.545
We were located in the equatorial southern current.

So wher’s Drifty ? see attached