Transmission leaking right after replacing

This morning I found transmission fluid on my garage floor where the truck had been parked overnight.

I cannot tell if the amount of fluid is "a lot", "some", or "very little". My very best judgment is maybe, one-eighth of a measuring cup.

I pulled out the truck, warmed it up, and checked the fluid level. The fluid level was fine.

I cleaned up the fluid at about 11:30 and went back out at about 2:00 p.M. There were two small puddles about the diameter of two silver dollars side-by-side.

The transmission was replaced out of state, so I cannot just drive down the block to make the mechanic look things over.

This vehicle has not ever leaked anything. Ever.

My questions are:

1. Should I take this in immediately?

Or

2. Is it common, or to be expected, that some residual fluid will "run off" or leak after a transmission is replaced? In other words, will this resolve on its own?

3. If "yes" to number one what is the more likely cause of the leak: (a) the pan, (b) a loose drain plug, (c) something else, (d) no clue?

Thanks.