ios7 safari (ipad) emoticon showing instead of glyphicon using bootstrap 3

Question

You can see below that some kind of native icon/emoticon is appearing instead of the intended glyphicon. However, the envelope icon is working fine. Icons also work fine on browsers, and on ios5. Seems a long shot, but does anyone know how to get around this?

I have already tried to change the character as per this question https://stackoverflow.com/a/19443169/558287

Answer 1

There seemed to be a conflict between my Glyphicons font version and the version of Bootstrap. Ensuring they were both from the same release (3.0.2) fixed it.