I guess there is a chance they made a floor like that but without seeing it, I'd cast another vote for blown I beams. Sounds like two blown I beams in the middle making the big hump, in tact I beams on either side of the big hump, then one more blown on either side of the intact ones creating the smaller humps. You should be able to see where the i beams used to be. At least it is symmetrically blown and shouldn't affect the tracking as bad as if they were all blown on one side.
It isn't the biggest deal to use as is but I would advise you run the floor soft. If the I beams on either side of the big hump blow, (which is likely if you put decent pressure in the floor, especially if it gets hot) the boat will be fairly unusable because you'll have one big hump that will damn near fill up the whole raft and it will teeter back and forth on the floor if you float it. Just remember that hump extends down into the water every bit as up and more so once you smash coolers and boxes down on it. It will draft low so pay attention to shallow rocks, sticks etc. that you would typically float over.
If there is water in the floor, which is likely, get it dried out ASAP. Don't let it sit inflated on a beach in the sun, especially black side up.
With that many blown I beams, if you brought it into the shop I would likely try and get you into a new floor if the tubes were in good shape.