So how did the Utah County Clerk’s Office fail to process — and lose track of — thousands of signatures on petitions seeking to put the Count My Vote initiative on the ballot?

“They had been put in the pile with the already worked packets,” County Clerk-Auditor Bryan Thompson wrote to Lt. Gov. Spencer Cox in a letter released Thursday.

In other words, Thompson said it was not the result of anything nefarious to hurt the initiative that is called, after all, Count My Vote. It was just a stupid mistake.

That comes a day after the office of Cox — the state’s top election officer — found a box of 105 petition packets that it said had not been processed. It sent them back to Utah County, and Cox also requested a written explanation about what happened.

Taylor Morgan, executive director of Count My Vote, says those packets contain thousands of signatures. Some come from state Senate districts where opponents said the initiative had fallen short of the required number of signatures after a campaign to persuade supporters to remove their names, according to Morgan.

Rick Egan | The Salt Lake Tribune Sharilyn and Gavin Grooms (left) chat with Tanner Leatham (right) as he gathers signatures for Sen. Curt Bramble, at their home in Provo, Monday, January 4, 2016.

Discovery of the box made the proclamations of victory by the opposition group Keep My Voice appear premature, and perhaps wrong.

Thompson’s letter to Cox seemed to suggest the error came as his staff was overworked, and that it deserved at least part of the credit for discovering the lost signatures.

Thompson noted his staff had worked hard on verifying signatures from initiatives “in addition to an Orem City petition, and multiple candidate petitions packets.”

He noted that Count My Vote officials asked his office on Tuesday “about some packets that they had submitted that did not appear to have been processed based upon preliminary reports in the system.”

He said his office compared its records to those of Count My Vote, “and determined that there was a possibility that some of the unprocessed packets may have been placed in a box with packets that had already been processed.”

Thompson said his office informed Cox’s staff about that possibility, as the records by that time had been shipped to the state Capitol for retention. Cox’s office then discovered the box full of unprocessed packets.

“Our staff has made it a priority to process those packets and enter them into the system,” Thompson wrote, vowing to complete that work by late Thursday.

Justin Lee, state elections director for Cox, said he has until June 1 to rule on which initiatives will appear on the Nov. 6 ballot. He said he expects no final announcements until just before that deadline.

Asked if Thompson’s explanation was satisfactory — or if Cox is considering sanctions or other action — Lee said, “We don’t have any comment on that at this time.”

To qualify for the ballot, initiatives need voter signatures equal to 10 percent of the votes cast in the last presidential election — a minimum of 113,000 statewide — and must achieve that percentage in at least 26 of Utah’s 29 state Senate districts.

Keep My Voice had waged an expensive drive seeking to persuade petition signers to remove their signatures, and targeted some districts in Utah and Washington counties.

Morgan has said his group figures another 50 packets in Washington and Iron counties have also disappeared, and have not yet been found. With the discovered missing signatures in Utah County, he said his group is confident the initiative will qualify for the ballot.

The initiative seeks to reaffirm two paths to the ballot for candidates: the caucus-convention system and/or collecting signatures. Supporters say their plan gives voters more choices. Opponents favor returning to the old system where a candidate could only get on the ballot by going through party caucuses and conventions.

Thompson wrote his explanation letter to Cox on Wednesday, when he had declined to answer press inquiries, saying he was too busy preparing for a property tax sale. Thompson was defeated in his bid for re-election this year at the Utah County Republican Convention after other gaffes by his office.

One of those occurred last year when the clerk mailed out 68,000 Republican congressional primary ballots to voters who weren’t registered with the GOP and, thus, were ineligible to vote in the election.