Manufacturing defects happen, products slip through QA, etc. This easily may have been a one-off error that just affected that one filter, and not a batch. I've been using Motorcraft (Purolator) filters for 24 years and have never had a failure, but it doesn't surprise me that one failed. It certainly won't turn me off of Motorcraft/Purolator filters.
Hatch Nation #90
'12 SE Sport 5Dr |╠╬╝|Sterling Grey Metallic|203a|Moonroof|17" Paint/Mach Whls|K&N 57S-4000|FFE RMM|Steeda STB, RSB|JBR bushings
'01 ZX3|╠╬╝|Pitch Black|Prem. pkg.|Moonroof|SVT Snorkel|SVT Springs|S2 Dampers|Steeda STS|Magnaflow exh.