First you download a .VPK extractor of your choice here:
VPK Readers.Then you go to common/counter strike global offensive/csgo/
in there you will find plenty of pak01_000.vpk files. Open them with your magical VPK reader.
Somewhere in there (probably materials/models/hostage or something) is your .vtf file for the hostage. Extract it and use
VTFEdit to change the .vtf to .tga or .png, then open it in paint, paint a smile on the hostage, he is about to get rescued, so he should smile a bit more.
Then import it in VTFEdit, save it as .vtf, place it in GSGO/materials/modelpath
And hopefully you will have happier hostages now.