thanks yeah I am telling platformio.ini to use a previous version of mbed, but I am certain this is not the exact version I was using before I reformatted. So I am trying to find that out through a macOS Time Machine backup. There is no suffix on the folder name.
This is the file structure of the package. Any idea where to find the version in all this? 
$ .platformio/packages/framework-mbed/
.astyleignore .travis.yml TEST_APPS/ events/ requirements.txt
.astylerc CONTRIBUTING.md UNITTESTS/ features/ rtos/
.coveragerc DOXYGEN_FRONTPAGE.md cmsis/ hal/ targets/
.gitattributes Jenkinsfile components/ logo.png tools/
.github/ LICENSE-apache-2.0.txt docs/ mbed.h
.gitignore LICENSE.md doxyfile_options package.json
.piopm README.md doxygen_options.json platform/
.pylintrc TESTS/ drivers/ platformio/