The 30-year-old was instead in Munich for a team bonding session at a beer festival under the instruction of Saracens officials.
And despite the prospect of the Premiership club being hit by a 5000 euro fine, Saracens chief executive Edward Griffiths insists the right decision was made.
"We look forward to resolving this matter with ERC, and playing our full part in a successful competition," said Griffiths.
"The decision that Steve Borthwick should attend a pre-arranged squad function was entirely the club's decision, and nothing to do with Steve.
"Nobody can doubt the professionalism and commitment of perhaps the most professional and committed player in the country.
"The clash of dates was unfortunate but, at the eleventh hour, we rationally decided it was more important for our captain to take part in a long-arranged and highly significant squad event."