On quering the blockchain, can someone read what transaction took place? Like considering the Alice Bob ex where Alice is the customer and Bob is the merchant. If Alice and Bob signed a contract where alice will pay bob on the delivery of a service. The transaction took place at time "t". 

Can some one query the blockchain at time "t+10" and see what was the actual contract signed between alice and bob?
We're implementing bitcoin-blockchain smart contracts in OpenBazaar.

OpenBazaar smart contracts are not part of the blockchain. The blockchain stores the multisig contract only; it serves as a depository for the money to stay before a product is delivered.

However, smart contracts are viewable at a later time, and either party can prove that the contract was in fact signed by their counter-party. Whether a public entity is able to view these contracts depends on how the contract was transferred between the two parties. Contracts are general means of exchange, so they can be transferred privately (e.g. via GPG-encrypted email), or publicly (e.g. by publishing plaintext on reddit).

In all cases, contracts are typically GPG triple-signed with public keys, and this signature is verifiable by anyone. If the physical identity of the person holding a GPG key corresponding to an OpenBazaar identity is known, they can be hold liable in traditional law court.

Of course, one of the points of OpenBazaar is pseudonymous transactions between merchants and buyers whose physical identity is not known. In that case, the contract may be displayed in a traditional court, but the court will be powerless. On the contrary, we employ arbiters and mediators that are able to resolve such conflicts of interest between pseudonymous parties, and who can themselves be also pseudonymous if they so desire.