Don't worry about it - there was a reminder of this in at least two of our internal PADI professional webinars this last year so PADI must be getting lots of questions on this very topic from shops! I wouldn't really know if that is on the website even.
In case it helps, I found the wording from the 2007Q2 Training Bulletin, the official communications that all PADI pros have access to:
Q How long does a diver have to complete a PADI course?
A There is no time limit as long as the student diver resumes training with the same instructor, or with another instructor at the same dive center. A PADI Referral is valid for one year (12 months) from the last completed training component (except Adventures in Diving and Specialty Programs which have no time limit on referrals); however, this is not the case for course completion. If there is a 12-month (or longer) break in training, have the student diver complete new administrative paperwork including a liability release, medical statement and Safe Diving Practices Statement of Understanding. Reassess and remediate where appropriate.
It should give you something to discuss with your dive shop in case they try to quote some (nonexistent) PADI policy on course expiry. They are obligated, in a sense, to help you complete the certification you already paid for. Certainly the best outcome would be a discount on a full course; alternatively, you may be able to work out a combination of pool check dive, extra dives, knowledge reviews, final exams, etc. with them. After all, they are responsible for your safety and readiness for open water dives, so they can legitimately ask you to do the remediation work.
I hope you can get to an arrangement that's good for both sides!