Sometimes what looks to be an error is actually what the record said. In the World War I Draft Card database at Ancestry.com, there are 22,975 results when a search is performed for men born in 1918 (Ancestry.com members can see search results here). While I have not looked at all 22,975 results, the ones I did look at had a year of birth of 1918. While obviously the card is wrong, the transcription is correct and theoretically, transcribers are to transcribe what the document says, even if the document is clearly wrong.
So maybe if you can't find someone in that index, consider that they information they gave is wrong, making the index entry problematic for you as well.