unfortunately, you haven't really given us a lot of information to go on. for instance, how long was the Oscar out of the tank for? how far did it fall to the ground? are there any signs of injury? you should also look at why your Oscar was able to jump out of the tank. Oscars do occasionally jump, I don't believe they are tried to jump out of their tank, probably investigating things they can see above the water, or under the tank lid. an Oscar tank should always have a secure lid , Oscar is a quite powerful fish say have to bear that in mind.
We've all heard of the expression "2's company, 3;'s a crowd" I believe this is no exception with the Oscars. If you had three Oscars and two of them decided to pair off and breed, it could result in quite serious aggression problems because a third Oscar could be looked upon as a threat. You also have to look at how big your tank is. Two Oscars require no less than 100 gallons, three Oscars would need at least 180 gallons UK to be comfortable