How to check if a certain Patch was applied to Oracle Applications instance using 'adpatch'?

Method 1
Check Patches applied from Oracle Applications Manager (OAM).
a) Connect to OAM:
http://hostname.domain:PORT/servlets/weboam/oam/oamLogin
Go to Site Map-->Maintenance-->Applied Patches
Enter Patch ID and press 'Go'
See if Patch was returned

Method 2
You might also use the following query, however methods 1 and 2 are more reliable.

SQL> SELECT DISTINCT RPAD(a.bug_number,11) RPAD(e.patch_name,11) RPAD(TRUNC(c.end_date),12) RPAD(b.applied_flag, 4) BUG_APPLIED FROM ad_bugs a,ad_patch_run_bugs b,ad_patch_runs c,ad_patch_drivers d ,ad_applied_patches e WHERE a.bug_id = b.bug_id AND b.patch_run_id = c.patch_run_id AND c.patch_driver_id = d.patch_driver_id AND d.applied_patch_id = e.applied_patch_id AND a.bug_number in ('','');ORDER BY 1 DESC;