Iran would not give the bomb, if they had it, to terrorists for two reasons. 1. Iran wants to be the one to chose the time and would not allow their clients like Hizbullah to pick the time. 2. Israel would immediately nuke Tehran if any terrorists group detonates a nuclear weapon in Israel, and Tehran know that. Thinking that Israel would hold back because they couldn't 'prove' a link to Iran is naive.
US rally shows support for ex-Marine held by Iran on spying charges (AP)
from the article: Insanity, not logic, guides Israel's leadership