[[!migxLoopCollection?
&packageName=`myPackage`
&classname=`myPackage`
&where=`{"title:LIKE":"%[[+search]]%","OR:description:LIKE":"%[[+search]]%","published":"1"}`
]]yeah, this should work, if you put the search-term into that placeholder.
You could also use a snippet, like getReqParam or a fastField-tag to get the search-term
there is a &emptyTpl - property