I would translate this to:
Even if I could meet you by chance,
I would never leave your hand a second time.
That is because of the following analysis: moshi, if; mo, even; kimi, you; ni, preposition required by meguriau; meguriaetara, -tara form of potential of meguriau, meet by chance; nido to, a second time; kimi, you; no, possessive particle; te, hand; wo, object marker; hanasanai, negative present of hanasu, let go of. Trouble is, I've seen translations of this, which is from Time After Time by Mai Kuraki, which translate it more or less as:
Even if I had met you by chance,
I would not have left your hand a second time.
But if hanasanai is present, why should I translate it with a past conditional? Wouldn't it make more sense to translate it as a present one? It is true that -tara contains the past suffix -ta, but so what? Does it necessarily imply a past action? And if so, why use the present in the apodosis?