In Islamic buy and sell.

1. The buyer and seller must be present under the same 'majlis'.
- Majlis refer to place or situation and bound by time which means the sale should be in present time.

2. The object of sale must be present.
- Self explanatory. But in your case, Ts; the object is not 'present' hence it creates doubt.

3. The object must be halal and faultless. Even if there is a fault, the object's fault should be notified first to the buyer.

4. The price of the object must be notified clearly.

there's more but can't remember at the moment.