No lab tests I'm afraid. The only way I have ever had of gauging my own IR is by how much my muscles hurt when they are not getting fuel through and how difficult it is still to lose weight. I need to stretch my muscles before I walk or work to help fight the insulin resistance. That's OK but boring and often too time consuming to do all the time. I am still producing my own insulin too. Not scientific I know, I just thought you would be interested in the weight lost during a hypothermic episode.
I have never been told I am IR, so I have had to assume that my slim build and inability to put on much weight was due to IR preventing glucose passing into the muscles for storage or use. It has never been measured by my GP.
Having said that, it is one of the warning symptoms of T2D that sudden weight loss and high bgl is part of diagnosis. another set of tests is used to prove that T2D has high levels of insulin with high bgl, and this is the pointer to IR. I don't think there is a specific human test, but some animal studies did use lab results as their proof for IR reduction.
Recent studies have claimed IR reduction is linked to fat stored in adipose tissue, and no doubt that study will describe methods used to validate their claim, but I have lost the link to that report.
Your weight reduction is a fine example of the brown cells doing their stuff, and it is probable that reducing IR actually allowed increased fat take up into the adipocytes to replace that lost through the shivering. So lower IR allows more fat storage, so it maybe that this counteracted itself and that is probably why you did not notice.