Question: Do you know whether there is any online site that shows US casualties or even soldiers, or sailors who served in World War I? I have a guy who filled out a draft card in Rumford, Maine in 1918, at 37 years old. He worked at the paper mill there. I can find no trace of him anywhere after that. Wondering if he was taken into the service, and either died in the war or was discharged/pensioned off years later somewhere and there might be a record of it. Seems odd that he would vanish like that.
If he was in fact a veteran, and was buried overseas you should find him on the American Battlefield Monuments Commission website: http://www.abmc.gov/search/wwi.php Do realize that if his body was returned for burial in the United States he will not show up on the above database.
You should be able to confirm if he ever enlisted in World War I from the records of the Adjutant General's Office in Maine. According to Peter Ogden of the Veterans Affairs Office in Maine these records have been transferred. They are now under the custody of the Maine State Archives - http://www.maine.gov/sos/arc/ Also, the Veteran's Officer in Rumford, Maine should have a record of the local veterans from World War I.
The existence of his signature on a draft card does not necessarily confirm military servce. NEHGS has all the Maine Death records that would cover the period between World War I and the 1920 or 1930 Census. These can be searched at our library and research center at 99 Newbury Street in Boston, or you can hire our NEHGS Research Service staff to search them for you at: http://www.americanancestors.org/research-services/