There are a lot of things going on here, so let me unpack them one by one. Taffy is very powerful and has a lot of functionality. It is worth the time. The examples on the other had also try to cover a lot of stuff. They kind of use a non standard approach to the directory structure.
Short answer
Based on your error message, one of two thing are happening, either ./Taffy/examples/api_LogToEmail/resources/savesLog.cfc
does not exist or it has a path mapping in <cfcomponent extends="taffy.core.resource" taffy_uri="/foo">
that is not resolving.
Long answer
I see that you are using Ortus CommandBox. (Shameless plug follows). I have written code and have code on how to do this. If you go to https://github.com/jmohler1970/Taffy_video , You can find the first video.
If you go to https://coldfusion.adobe.com/profile/jamesmohler and click on blog, you will find eight videos on this very topic.
Some code
Over on, https://github.com/jmohler1970/Taffy_video Taffy,
Consider the following directory structure:

box.json has
{
"dependencies":{
"taffy":"git://github.com/atuttle/Taffy.git",
"formutils":"git://github.com/jmohler1970/FormUtils.git",
"northamerica":"git://github.com/jmohler1970/NorthAmerica.git"
},
"installPaths":{
"taffy":"taffy",
"formutils":"formutils",
"northamerica":"db_setup"
}
}
Note in the code that Taffy is no where to be seen. We have a very clean structure. Taffy has not been applied to it yet. This is a good thing. Because I know where Taffy in a more normal way. I don't have to wonder why the examples are the way the are. I can just worry about my own code.
application.cfc
component extends="taffy.core.api" {
...
this.mappings['/resources'] = expandPath('./resources');
this.mappings['/taffy'] = expandPath('./taffy');
This is where I get the mappings to work. This is likely different from the Taffy examples, but is much closer to what you might use in a production environment