National Highways says bad weather meant asphalt-laying work had to be delayed.
National Highways estimates 30,000 motorists use the stretch in Norfolk.
Chris Griffin says workers have to get through a "tricky winter" to finish on time.
Business owners say shutting both junctions to a village road for roadworks could be "devastating".
Norfolk Police says the theft took place between 06:55 BST and 07:30 on Tuesday.
A former Green councillor says he may go to the Supreme Court over three road schemes in Norfolk.
Dr Andrew Boswell is fighting three planned upgrades to the A47 in Norfolk.
Environmentalist wins right to appeal legality of three major road schemes in Norfolk.
Three schemes will see two more sections of the road dualled and the redevelopment of a junction.
