Hi
After starting to succeed in gradually getting rankings for a client
in a competitive sector, last month, we accidentally uploaded a
robots.txt file that disallowed all robots.   Yes, I know, stupid
beyond belief, but it's done now...
This month, although the pages are still in Google's index, (site:url
shows 188 pages) their cached versions have been deleted and all
rankings have disappeared.
We have now uploaded the correct robots.txt file and re-submitted the
site to Google (though there are plenty of incoming links anyway).
I need to know how to handle this with the client, so I need someone
who "knows" or has experience of the same thing.   So can you tell me:
1) Are we likely to have caused a major problem ("Sandbox" or not) and
will be starting from scratch with building up rankings, or can I tell
the client with confidence that this is just a one-month glich?
2) Is there anything we can do to "speed up" the process of getting
the pages restored? (Probably not, but anything that's worth a try...)
We have a pretty good track record with SEO, but have never done
anything this dumb before, so the price has been set for someone who
can provide some genuine help in how we deal with this.

Sticky situation,

Basically, you won't get sandboxed for your robots.txt file. You may
have however caused the SE spiders to stop visiting your site (for an
extended period). I would start by generating some new anchor text
backlinks from relevant similar sites.

Are any of the bots landing in the log files? Backlinks will help.
Don't submit to Google (or any other SE's) if you are indexed already.
Make sure the site has not been infringed upon (thus triggering
duplicate content filters). You can check here:
http://www.copyscape.com.

New content (articles etc...) will help. It may be a good time to
revisit link structure. If you need further assistance, you can visit
me at http://www.optimalwebconsulting.com. Email me and I will see if
I can assist you further. Good luck!