A couple of comments. First, If the ice did not end up with a large air gap between it and the water I would agree that you are holding the water. When I had my house built the septic leach field trenches were dug and then we got hevy rain that filled them to the top followed by a deep freeze. The water froze solid on the top but the ice quickly broke apart since the trench drained rapidly as you would want for a leach field.

Second, There is a bit of a leap of faith when doing a pond. My best advise on that is that if you geet to know the "pond guy" and have a good feeling about him them go for it. If not find, someone else or don't do it. Depending on the situation the project could take a long time to finish. Also, you need to share the same vision as to what the pond is all about so that you can participate in the creation of the pond, even if it's just with input on the design. This is not like building a house where there is a fixed design. It is often design on thee fly depending on what they find once they get deep into the project.

Good Luck!