As long as we are speculating, I'll throw in.
I remember working a job a few years ago and getting a tingling leaning up against a drop ceiling grid. The grid was isolated from the other grid by the four drywall walls of the office. The 2X4 lay-in wasn't grounded and my meter showed slight voltage to ground (I think I used a sprinkler pipe). shut the light off, no trickle. Ground the light, problem solved.
Also my parents have fluorescents that intermittently start in hot, humid weather. They are ungrounded, and after having my memory jogged by this post, I need to fix that. It will probably stop the sluggish start (I've already replaced the ballasts).
As to the ungrounded desk lamps, are those twin tube? maybe the field cancels itself out as it doubles back, (similar to the requirement in having both conductors present in the 300-3(b) requirement.)