A virtual font is a set of instructions which basically refer to characters in other, non-virtual fonts. Virtual fonts permit you to make a single font by combining characters from one or more non-virtual fonts, without duplicating the characters from the non-virtual fonts.
Virtual fonts have the extension
.vf when compiled. This format is the format TeX uses but is not human-readable. Virtual fonts have the extension
.vpl when in human-readable form. It is possible to convert from VPL to VF and from VF to VPL. However, human-readable information is typically lost when converting from VPL to VF, so that converting VF back to VPL produces a less easily read file than the original. Comments and meaningful designations get stripped.
This is why working from a log file which list the PFBs is probably the easiest way to locate the font containing the characters of interest, at least when you are interested in a single character.
The best way to do it is probably to create a file which contains only the character of interest. That way, you reduce the number of PFBs used and reduce the risk of identifying the wrong instance of that character. Obviously, you need to ensure that the document uses the same font size and font configuration as your real document. But make the content minimal.
cmsy10.pfb is the font of interest.
I could open the PFB in FontForge, as suggested in comments, but it may be less hassle to just read the corresponding AFM,
fonts/afm/public/amsfonts/cm/cmsy10.afm which includes
C 33 ; WX 1000 ; N arrowright ; B 55 -11 943 511 ;
as well as the basic data for the font as a whole, in case you need that
Comment Creation Date: Mon Jul 13 16:17:00 2009
FamilyName Computer Modern
Notice (Copyright (c) 1997, 2009 American Mathematical Society (<http://www.ams.org>), with Reserved Font Name CMSY10.)
FontBBox -29 -960 1116 775