I wouldn't say that there was anything wierd about the hood necessarily. The "De Lorean" badge on it was not standard for the VIN, and nor was the flat hood (I think?) - so, yes quite possibly the hood has been replaced - which could just be a case of replacing the old one due to minor damage. This is what a "new" hood looks like.
Whether or not there is actually a gas flap in it I can't tell from that photo - it could just be a reflection. Or if it is there then it is a fairly common modification now to cut a flap in any hood. It makes filling up a lot easier!