I don't think you can do this with dynamic stats (the
type of report where you configure fields for columns,
filters, etc. from OTRS's agent web interface ->
STATISTICS module).
You can do it with static stats if you know some minimal
Perl, SQL and how to integrate a new Perl file into OTRS as
a backend for a static stat report. If you know SQL but not
Perl then you can forget about integrating the report into
OTRS and just run a query on the OTRS database and export
its results in Excel.
For the query you need to select from table "ticket" those
entries not having corresponding entries in table
"ticket_history" with their "create_time" column within the
last 2 days and their "history_type_id" column = "2" (2
corresponds to a "FollowUp" history entry type).
OTRS registers a history entry of type "FollowUp" whenever a
customer posts a reply to a ticket through his web interface
or via email. You need to decide your definition of "follow
up" is the same. You will also need to add to the query
references to a lot of simple dictionary type tables to get
actual human readable values for things like ticket's queue
name, service name, owner, etc. This last part can be covered
by just looking at the database tables and making common sense
assumptions.