The experienced central defender is out of contract at the end of the month after refusing a new deal at Everton.
He told www.evertonfc.com: "I got a phone call from Bolton to tell me they were pulling out of the deal as the board of directors weren't prepared to sanction it.
"Myself, the manager at Bolton (Sam Allardyce) and everyone connected with the transfer are all obviously frustrated.
"These things can happen from time to time. Now I just have to focus on my future."
Unsworth initially rejected a one-year contract at Everton. A two-year deal followed but by then he was already involved in dialogue with the club's Premiership rivals.
A Bolton spokesperson said: "We have failed to agree personal terms with the player."
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