Do we have any evidence, or at least a historical guess, as to what happened? It seems really odd that 2,000 ships, along with the emperor of Mali, would just straight up disappear.
Considering they sailed from the west coast of Africa, could they have reached America?
I don't think it would be correct to say "Mansa Musa claimed that..."
When this claim enters the historical record, it is not written in Musa's hand, or even in his lifetime.
We first encounter this claim when the Syrian writer Shihab al Umari visits Cairo 20 years after the Malian emperor's hajj, and al Umari writes down accounts of Cairenes who interacted with the Mansa during his stay in that city.
So, there is already a fair amount of room for invention being injected into the narrative, either by al Umari, or by one of the people he interviewed.
All of this is to say, we can not be certain that there was a voyage. We can't be certain how many boats were taken. The existing oral traditions and the earliest written account of the dynastic succession of Mali (written by Ibn Khaldun) don't agree with al-Umari whether Abu Bakr II was the father or elder brother of Musa. In fact, a recent(ish) scholar has even proposed that references to an Abu Bakr II might stem from mistranslations of arabic and misunderstandings of the rules of Malian inheritance. Thus, this scholar proposes that Mansa Musa was not "son of Abu Bakr II" but rather a male descendant of Abu Bakr I.^1
All of this is a long way of saying, we don't know much at all about this voyage of Abu Bakr II beyond what al Umari tells us, and there is strong reason to suppose it might be myth.