Sobek already had 26,000 experience points, but he needed 90,000 to level up. Staying in the vicinity of the oxalaias' nest he could have obtained several new points in just a few days, but when he returned to their islet he found that the oxalaias were already gone.
Unfortunately, what he had feared had happened: feeling in danger, the oxalaias had taken their cubs and ran away all together. Sobek had done his best to not frightening them, but the arrival of the poachers had changed everything. While humans would most likely never return, at least not for a long time, the oxalaias had no way of knowing this, and no animal would have remained in a place where it felt in danger.