Brits say "reckon", but it doesn't sound the same as when a US Southernor says it. Maybe the froggie learnt English English.
Reckon could also be a taken as a loose cognate of the French verb "reconnaitre" which means "recognize", but with the sense of understanding more than visual recognition. If the froggie policeman was saying, "We understand now that it was probably pirates" that did it, he might well have used the term "reconnais" which the English language press might have rendered as "reckon".
A victim of dead reckoning, do ya suppose?