How to reproduce:

0. configure sks keyservers

1. gpg2 --search-keys 0xDB068FA97889A60F0A0D615BD5E0B342C6B115B5
2. gpg --search-keys 0xDB068FA97889A60F0A0D615BD5E0B342C6B115B5

Expected output:

gpg2 and gpg both return the same search result, i.e. one key found.

Actual output:

1. gpg: error searching keyserver: No data

gpg: keyserver search failed: No data

2. (1) Tilo Jung <tilo@jungundnaiv.de>

	  2048 bit RSA key C6B115B5, created: 2014-01-02, expires: 2018-01-02

Keys 1-1 of 1 for "0xDB068FA97889A60F0A0D615BD5E0B342C6B115B5". Enter
number(s), N)ext, or Q)uit >

In contrast to that, just searching with the short key id with gpg and gpg2
works as expected, i.e. in both cases a match is returned:

gpg2 --search-keys 0xC6B115B5
gpg --search-keys 0xC6B115B5

Looking at the verbose output of gpg and dirmngr (when using gpg2) it seems that
the difference is that gpg2/dirmngr strips the 0x print from the fingerprint
string when constructing the https URL. GPG 1 doesn't do that.

For example URL from the dirmngr log:

https://keys02.fedoraproject.org:443/pks/lookup?op=index&options=mr&search=DB068FA97889A60F0A0D615BD5E0B342C6B115B5

with curl:

$ curl
'https://keys02.fedoraproject.org:443/pks/lookup?op=index&options=mr&search=DB068FA97889A60F0A0D615BD5E0B342C6B115B5'

-> 404, no keys found

When patching that Url with a 0x fingerprint prefix:

$ curl
'https://keys02.fedoraproject.org:443/pks/lookup?op=index&options=mr&search=0xDB068FA97889A60F0A0D615BD5E0B342C6B115B5'
info:1:1
pub:DB068FA97889A60F0A0D615BD5E0B342C6B115B5:1:2048:1388670492:1514900892:
uid:Tilo Jung <tilo@jungundnaiv.de>:1388670492::

And with gpg 1, enabling verbose logging like this:

gpg -v --keyserver-options=debug --search-keys
0xDB068FA97889A60F0A0D615BD5E0B342C6B115B5

I can verify that the internally generated URL indeed has the search=0xDB... part.