Sounds like someone dropped the ball, here's what the ATF says about background checks.
Tim
http://www.atf.gov/firearms/faq/faq2.htm#p34(P34) Will NICS provide an instant response? [Back]
NICS will not always provide an instant response. Licensees will receive either a “proceed”, “denied”, “delayed”, or “cancelled” response from NICS. If a “proceed” response is received, the transfer may proceed. If a “denied” response is received, the transfer may not proceed. If a “delayed” response is received, the transfer must be delayed until a “proceed” response is received from NICS or until the lapse of 3 business days, whichever occurs first. Of course, the licensee must still comply with any waiting period requirements under State law. See Question P29 for a discussion of cancelled transactions.
(P35) For purposes of the Brady law, what is meant by a “business day?” [Back]
A business day is defined as any day on which State offices are open.
(P36) If a licensee contacts NICS on Thursday, December 2, and gets a “delayed” response, when may the licensee transfer the firearm if no further response is received from NICS? [Back]
The firearm may be transferred on Wednesday, December 8. Assuming State offices are open on Friday, Monday, and Tuesday, and closed on Saturday and Sunday, 3 business days would have elapsed at the end of Tuesday, December 7. Therefore, the licensee may transfer the firearm at the start of business on Wednesday, December 8. The 3 business days do not include the day the NICS check is initiated.
(P37) What should a licensee do if he or she gets a “denied” response from NICS or a State point of contact after 3 business days have elapsed, but prior to the transfer of the firearm? [Back]
If the licensee receives a “denied” response at any time prior to the transfer of the firearm, he or she may not transfer the firearm.
[18 U.S.C. 922(d)]