Did they buy Iranian, or where whey acting on Tehran's behalf?
Pardon the pun but Tehran is unlikley to be calling the shots on this one for two reasons: Firstly
Israel came to the Lebanon, so the attack on the ship was hardly pre-meditated in the same fashion as an embassy bombing. This was tactical, not asymmetric. Secondly, I would suggest that Hezbollah probably don't need much encouragement to shoot at anything Israeli.
That's not to say several countries don't want to see the back of Israel and several may very well be providing at least funding. I would suggest Iran is implicated in the same way Tonga is in bombing Iraqi marketplaces in Iraq - by association. Our own club is just branded as the War on Terror.
Oddly enough, organisations like Hezbollah probably won't have as many 'respectable' companies banging on their door to supply arms, so they have to rely on less reputable vendors like Iran over BAe etc. But in the Gulf region I don't think ownership of arms is unreasonable; the visiting Israeli hardware provides an ironic endorsement for buying the stuff in the first place, irrespective of the legitimacy of its reason for popping in.