Personally a bit skeptical of this "...we don't know where the HEU has gone..." line.
For a long time now US IMINT platforms (both UAVs and things that fly or orbit at higher altitudes) have had the ability to
`stare' at large areas of the earth for long periods
and record what they see in exquisite detail. If something happens at a particular point, you can then re-wind the view, zoom in on parts of the picture, tag items of interest and then follow them back on the timeline.
Want to see where the truck carrying the bomb came from? Tag it, and follow it all the way back to the terrorist hideout.
Have never seen it (for obvious reasons) but have seen reports from those who have who say it is quite extraordinary.
As an area of great interest, particularly in the last few months, I would imagine there would have been a RQ-180 or some other HALO platform that we might not yet know about over Fordow for a long time, recording stuff almost continuously, and occasionally supplemented by U2s looking in from Iraq when needed and/or IMINT or SAR birds as they transit overhead.
I would have assumed that anything leaving Fordow recently would have been recorded by our friends in Chantilly VA - including where it went. I find it hard to believe it wouldn't have been.
But I may also have been reading too many Tom Clancy novels...