She asked her son to put her slip into the box for her and somehow his favourite Lego figure went in with it.
When she discovered what had happened she asked the presiding officer to help.
But with General and local election counts to carry out there was no guarantee that the figure would be found by Doncaster Council’s busy staff.
The polling day drama meant that it was not just Ed Miliband who was eager to find out what was inside the ballot boxes in Doncaster North.
The story had a happy ending as after results were all declared election staff rooted through the empty ballot boxes and found Carter’s toy.
And today the four-year-old went along with his mother to Doncaster Council without knowing that the figure had been found.
Instead staff let him peer into one of the discarded ballot boxes and discover it for himself.
His mother Olivia said: “He was so happy. He ran over to me and said ‘I love you so much’ I had to try hard not to cry. It was very emotional.”
She had gone to vote with her two children Carter and Honey, aged two, at Scawsby Community Centre on Thursday.
“I had three votes to fill out so I thought it would be nice to let my two children put the papers in the box for me. I was voting but when I looked over to Carter his face had gone white and he was crying his eyes out because the Lego man had dropped into the box.”
Mrs Allen, 23 from Scawsby, said she asked for help but as time went on over the weekend she was beginning to give up hope that the toy would be found.
But when she called Doncaster Council yesterday she got the good news.
“The officer said had she could put a note in the box to tell people this had happened but I thought it would just get lost or thrown out. I couldn’t even replace it because its a figure Carter has made himself with different parts from the Lego movie. He calls it ‘Star Wars man’.
“He hasn’t let go of it since we got home.”
Doncaster Council staff also gave him extra lego gifts including a Spiderman car as a present.