Speedbrakes are armed prior to landing on all 747's. This is confirmed as part of the Landing Checklist. Once the weight on microswitch system detects an 'on ground' condition, the spoilers should automatically deploy. This is normally confirmed by the non flying pilot. If they do not deploy, they can be manually selected by pulling the lever aft ( much easier for the Captain). If they do not deploy and the lever is NOT pulled back, you have no ground spoilers and your landing roll will be longer. You do not deliberately land a 747 without deploying the ground spoilers one way or the other.
Therefore, by definition, they were either unserviceable ( very unusual) or somebody owes somebody a beer!