Lamb appeared at a Rugby Football Union disciplinary hearing in London on Tuesday charged with striking, contrary to Law 10.4(a), following his sending-off alongside Gloucester prop Koree Britton.
He pleaded guilty to the charge and the panel judged the entry point for sanction was a low-end one (two weeks) before mitigation. He received a one-week ban and is free to play again on October 8.
The club will now, as a matter of course, hold an internal disciplinary hearing and expresses its gratitude to the RFU disciplinary panel for a fair and respectful hearing.
Britton contested the charge but was found guilty and the panel judged the entry point for sanction was a mid-range one (five weeks) before mitigation. He was suspended for four weeks and is free to play again on October 29.
The cases were heard by Sir James Dingemans (chair), Jeremy Summers and Dr Julian Morris at the London Bloomsbury Holiday Inn.