I have a purging SQL which deletes records from a single table prior to a certain number of days:
delete t1 where status in ("ERR","COMPL")
and datediff(dd,LastProcessDate,"datetime variable derived from getdate()") > 103

now I have run update stats on this table and have a non clustered index on both status & LastProcessDate.
The problem i am getting is when i do showplan:

This query is doing a tablescan. What i found is the following:
QUERY PLAN FOR STATEMENT 1 (at line 1).

STEP 1
The type of query is SELECT.

FROM TABLE
t1
Nested iteration.
Table Scan.
Forward scan.
Positioning at start of table.
Using I/O Size 16 Kbytes for data pages.
With LRU Buffer Replacement Strategy for data pages.

Total estimated I/O cost for statement 1 (at line 1): 244910.

but when i again ran this with a force index on the Status & Process date index , i got :

STEP 1
The type of query is SELECT.

FROM TABLE
t1
Nested iteration.
Index : StatusCode
Forward scan.
Positioning at index start.
Using I/O Size 2 Kbytes for index leaf pages.
With LRU Buffer Replacement Strategy for index leaf pages.
Using I/O Size 2 Kbytes for data pages.
With LRU Buffer Replacement Strategy for data pages.

Total estimated I/O cost for statement 1 (at line 1): 1025126.

Anyone have any idea regarding the optimiser behaviour in this case. Appreciate any help received.