There was so much going on in Niger 1999 that it is difficult to understand how such an intrepid intelligence gatherer as J Wilson (yes, saracasm) could have missed it.
Not only did Wissam al-Zahawi visit Niger in early February, but Dr AQ Kahn flew in from Sudan for a visit to Niamey (capital of Niger) at the end of February. (http://www.kashmirherald.com/featuredarticle/khanandbinladen.html ).
AQ Kahn returned to Niger in February 2000 (same source).
....and of couse to that should be added the incident that Wilson actually did report on; the businessman who in June 1999 tried to make contact between the new post-coup Nigerien government and Iraq.