Thank you John for using Ask Extension. I hope you'll find the following information useful.

For clarification, as a Master Gardener volunteer, I use science-based research to answer questions.  After an extensive search, I wasn't able to find any scientific information on Irish Spring soap and deer.  However, I did find numerous articles with anecdotal evidence about using soap as a deer repellent. Anecdotally, it was mentioned that while small wildlife like rabbits, squirrels and rats are repelled by Irish Spring soap, Opossums are unfazed.  So my guess, and only a guess, would be that the Opossum was carrying your soap bars.

I've enclosed several articles that discuss Deer-Proof gardening that I hope you will find helpful. 

The Elusive Deer-Proof Garden | Paulding County Horticulture News and Master Gardener Volunteers information (osu.edu)

Deer Repellents — Yard & Garden Report (ndsu.edu)

Thank you again for utilizing Ask Extension and good luck with your tulips.

It was a very interesting question.  Good luck with the tulips.