When it came to voting in Edmonton's municipal election, Kayle Clark thought he'd mail it in.

The 28-year-old spends a lot of time working out of town doing environmental field work, so he requested a special ballot from the city.

The special ballot process gives people who can't get to a polling station the opportunity to cast their votes.

"I completed it according to the instructions and put it into the envelope they provided," he said. 

"That has a pre-printed address, a prepaid envelope. And I dropped that off at a Canada Post location, which I assumed meant it was going to be mailed to the city."

'Why did I get this back'

When he returned home a few days after the election, he found the envelope in his mailbox instead of at Elections Edmonton where it should have been.

"I was confused at first, like, 'Why did I get this back?' I mean, it's a prepaid envelope, it has the address clearly written on it.

"I don't understand how this ended up back in my mailbox. Then I got angry at Canada Post for not actually delivering it." 

Clark immediately called Canada Post to complain about the violation of his democratic rights.

He was told the sticker on the prepaid envelope he used was scanned as undeliverable and the likely explanation was that it had already been used.

It's something that rings hollow with Clark who's disappointed he didn't get to vote.

"When I spoke to them on the phone, I think what made me most angry was the customer service person," he said.

"They kept saying, I'm sorry for the inconvenience. And that just kind of struck me, because voting is not a convenience it's one of those civic duties. There are people in other countries that have violence or die trying to vote, so calling it an inconvenience that my vote didn't get counted seems to miss the whole point." 

'We feel very bad that this happened'

Iain MacLean is director of elections with the City of Edmonton.

He said more than 1,000 special ballots were requested this election, with 644 actually returned.

"Of all the special ballot applications we received, this is the only one we've heard of that was sent back to the sender," he said.

"We feel very bad that this happened to this individual, but Canada Post is investigating to see what happened in the process that it was sent back to his residence."

Canada Post's investigation found the envelope was returned to Clark in error. 

In a statement to CBC News, the postal service apologized for what it called an isolated incident and said it is following up internally to ensure it doesn't happen again.

The city said it, too, will look at all its processes to ensure they offer residents the most efficient opportunities to vote. 

Clark said the only reason he found out his ballot wasn't counted was that he put a return address sticker on his ballot envelope, which isn't required.

He said he's worried there may be others who didn't do that and therefore wouldn't know if their ballots were processed.

He wants Canada Post and the city to make sure the problem doesn't happen to anyone else the next time Edmontonians go to the polls.