Is it reasonable for authors and editor to ignore review comments without explanation?
Remember, your view of the process is incomplete. Don't jump to conclusions. For example, this could've happened: the editor sent the manuscript for revision, which the authors took a few weeks to perform. The editor was able to check the revision without needing your help, so they made a decision without inviting you to review the revision. You mention that given the "very short time" between you submitting the review and the decision, the paper must've been accepted without revisions, but "a few weeks" is not a short time.

Another, more drastic possibility is, during the review period the lead author died, and the none of the remaining authors were sufficiently motivated to perform the necessary controls. The paper then became a "either you publish this or it'll go unpublished" paper and the editor made the judgment call to publish it (you did say the work is valuable!). 

I suggest saving your anger until after the paper is published. You can read it then and compare against the version you have. If you indeed find that the editor ignored your review, you can write to the editor then asking why they ignored your review.