Unable to replace HTML ampersand entity

*Note: $ symbol in this comment is actually & symbol, but strings are getting autoreplaced.

Some image files with the literal ampersand character (&) got encoded in WordPress as $amp;. This broke SiteSucker for some reason.

File names were of form file_a_&_b.jpg and were stored in post table as file_a_$amp;_b.jpg.

I did a search and replace with following strings:
Search: _$amp;_
Replace: _and_

It found the posts in question and many other false positives (for example url strings which had get arguments separated by ampersand).

When I initiated replace, nothing was actually change. I verified by rerunning search, and same search result numbers came back (i.e. assumed no change). Visual verification also indicated no replace took place.

http://ww.wp.xz.cn/extend/plugins/search-and-replace/