The article says it is the Kellogg's Jeff Tracy figure and I'd say they are spot on given this picture of it matches even the green https://www.picclickimg.com/d/l400/pict/173295240981_/Thunderbirds-Kelloggs-Figures-Jeff-and-Scott-Tracy.jpg
I had a green Kelloggs Jeff Tracey figure. I don't know what happened to it, but I know I never took it to the seaside!
Hugh's amazing Small Scale World to the rescue: http://smallscaleworld.blogspot.com/2009/01/t-is-also-for-thunderbirds-are-go.html
Its obvious what happened. When the Thunderbirds boys never came back for the last time and he was left behind on Tracy Island with only Brains he just swam for it!