Why on earth would Syria be the end recipient of the arms coming from Iran. Syria is not under any military embargo. Remember, this is the same nation that is in the process of purchasing Russian S-300 SAM batteries. A few hundred tons of ammunition, rockets and grenades aren't going to be a major issue in terms of sourcing. Which means that there's little reason for Iran to take the risk to ship such mundane weaponry. It also certainly wouldn't be a reason for covering up the merchandise, either physically or on the manifest.
Syria denies targeting refugee camp; UN condemns "murderous attack" (Reuters)
from the article: Israel releases arms ship said destined for Hezbollah