If it's a hoax, then it's probably a brother and sister (and maybe another sibling, who took the picture) who did it as a joke and accidentally dropped the photo -- why would they purposefully leave it in hopes of getting people riled up, in 1989? It's not like there'd be immediate news coverage, or anything that they could look at necessarily with the technology of the time. So, if it's a hoax, it's awfully weird why these kids would do such a thing in the first place. And, as mentioned, if it were a hoax then you'd think someone who knew the hoaxers would come forward.
And, of course, they would hardly know who Tara Calico was, or most other missing kids, in order to purposefully stage it with that intent.
I think it is real. There are a million reasons why we don't know who the kids are yet; it's also perhaps more likely that they were abused by a family member, and so never abducted in the first place. Sad, but it's a sad world. The expressions on the boy and girl's faces look quite unnervingly "real" to me.
Just a few thoughts in response to your post:
1. If the picture is real, why would they leave it behind and draw the attention to law enforcement?
2. I can think of one good reason why a hoaxer would not come forward- fear of getting into trouble.
3. The kids look remarkably clean. There are no signs of bruises, the clothing is free of stains and the boy looks like he recently has his hair trimmed. They do not look like they've suffered years of abuse.
4. I think that many people saw the picture and thought they looked like some kids that they knew but never reported it because the kids were still in the area riding bikes, hanging out, etc. I think people were looking for 2 missing kids instead of looking for 2 kids who may/may not be missing.
5. Kids do weird things all the time. The boys in the Johnny Gosch hoax pictures were trying to enter a contest.
"“I literally could not breathe. I could not get my breath,” Gosch told Channel 13′s Brilbeck. “I was so totally unprepared to see something like that. All these years had gone by and here was this picture.”
The image in question depicted a young boy, hog-tied and wearing only his underpants and socks.
Gosch took the photos to the West Des Moines police department.
“When I did we spread them out and the detective kept saying ‘That’s Johnny, that’s Johnny,’” said Gosch. “I said ‘I know that’s Johnny.’”
The press went wild. Newspapers and television stations across the country reported Gosch’s story. Then came a call from the West Des Moines police, who told Gosch they were planning a press conference of their own; they planned to announce the pictures weren’t of Johnny after all.
“I said that picture is Johnny, and the detective said to me, ‘Well, somebody from Florida called in and said he used to be an investigator and remembered the pictures — those pictures — from a case in 1970-something,’” Gosch said.
Noreen Gosch said she asked the detective if the caller had provided them with any evidence, and he’d responded with ‘no,’ telling her they just had the phone call.
“And based on his phone call you’re going to do a press conference and say that picture’s not Johnny?” she recalled asking him. “And he said, ‘Well, yes I am.’”
To this day, Gosch believes the boy in the photo is her son, and that he was bound, gagged and abused, and taken for the purpose of satisfying pedophiles. Police continue to insist it’s not him.
“We found out where the photos were taken,” Lt. Miller told Brilbeck. “We talked with investigators in Florida and they were able to identify all of the kids in that picture and they weren’t Johnny Gosch.”
http://iowacoldcases.org/case-summaries/johnny-gosch/