A weather balloon doesn’t have a contrail. Especially one that is that big, that thick and that dense.
Iran has submarine ICBM capability too.
European Missile Defense: Assessing Iran’s ICBM Capabilities
The Nodong-B reportedly uses technology from the Soviet-era SS-N-6 submarine-launched missile and has a range of 2,500-4,000 kilometers. It is reportedly shorter and wider than the original Nodong and has a dual-chamber control engine rather than the steering vanes of the original Nodong, which would make it more stable, more maneuverable, and more accurate than the original. Its Iranian derivative is sometimes called the Shahab-3B. Press reports in April 2006 noted that Iran had received this Nodong-B missile from North Korea, but it is unclear as to how many missiles were supplied and whether Iran is also indigenously building this missile.
http://www.armscontrol.org/act/2007_10/Mistry
What if there was a little boy in the balloon.