If I I goto http://www.mydomain.com/images/notHere.gif according to the logs it looks like it gets rewritten sometimes. However in the browser I just get a 404 trying to goto that image. Is this the proper code?

rewriteCond %{REQUEST_URI} !-U
rewriteRule \.gif$ /images/NOthumb.gif [L]


REWRITE LOG:
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#834b220/subreq] (4) [perdir /var/www/html/images/] RewriteCond: input='/images/notHere.gif' pattern='!-U' => matched
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#834b220/subreq] (2) [perdir /var/www/html/images/] rewrite 'notHere.gif' -> '/images/NOthumb.gif'
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#834b220/subreq] (1) [perdir /var/www/html/images/] internal redirect with /images/NOthumb.gif [INTERNAL REDIRECT]
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#820ddf8/initial] (5) RewriteCond URI (-U) check: path=/images/notHere.gif -> status=200
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#820ddf8/initial] (4) [perdir /var/www/html/images/] RewriteCond: input='/images/notHere.gif' pattern='!-U' => not-matched
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#820ddf8/initial] (1) [perdir /var/www/html/images/] pass through /var/www/html/images/notHere.gif
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#820fe00/initial] (3) [perdir /var/www/html/images/] strip per-dir prefix: /var/www/html/images/notHere.gif -> notHere.gif
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#820fe00/initial] (3) [perdir /var/www/html/images/] applying pattern '\.gif$' to uri 'notHere.gif'
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#834b220/subreq] (3) [perdir /var/www/html/images/] strip per-dir prefix: /var/www/html/images/notHere.gif -> notHere.gif
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#834b220/subreq] (3) [perdir /var/www/html/images/] applying pattern '\.gif$' to uri 'notHere.gif'
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#834b220/subreq] (4) [perdir /var/www/html/images/] RewriteCond: input='/images/notHere.gif' pattern='!-U' => matched
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#834b220/subreq] (2) [perdir /var/www/html/images/] rewrite 'notHere.gif' -> '/images/NOthumb.gif'
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#834b220/subreq] (1) [perdir /var/www/html/images/] internal redirect with /images/NOthumb.gif [INTERNAL REDIRECT]
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#820fe00/initial] (5) RewriteCond URI (-U) check: path=/images/notHere.gif -> status=200
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#820fe00/initial] (4) [perdir /var/www/html/images/] RewriteCond: input='/images/notHere.gif' pattern='!-U' => not-matched
[23/Jul/2007:16:19:39 --0500] [www.mydomain.com/sid#81d9660][rid#820fe00/initial] (1) [perdir /var/www/html/images/] pass through /var/www/html/images/notHere.gif