using the search feature in the handheld skin will change the selected player 
back to the default one. this prevents you using the search feature for any 
player other than the default one. 

the problem happens on the search results page - the links on the returned 
item list have the mac address of the default player, not the one currently 
selected.

the cause appears to be the hidden mac field in handheld/searchinput.html 
(line 19):
<input type=hidden value="[% player | uri %]" name="player"> 
which produces a mac address with '%3A' instead of colons

if you change it to 
<input type=hidden value="[% player %]" name="player">
the mac address has colons and the problem disappears - you can now search and 
add tracks to the playlist for a non-default player