There is a table called AUDITRECORD
in DB which has the details about all the events happened it includes Delete event. But the information will be available only if you have configured Audit Event Recording.
If you have configured then you can get the details by using below query.
select * from auditrecord where eventlabel='Delete';
Refer Windchill helpcenter for steps to configure audit event recording.
In case you have not done this configuration and still wants to fetch the data about deleted objects then
Apache Web server logs and looking at backup of database or current
database doing a negation query to match part object identifer in
apache logs against those still remaining in database. Lot more work,
but not impossible.