query planner not using the correct index

This query is run on a test system just after a backup of the database
has been restored and it does exactly what I expect it to do

EXPLAIN ANALYZE SELECT foos.* FROM foos INNER JOIN bars ON foos.id =
bars.foos_id WHERE ((bars.bars_id = 12345)) ORDER BY attr1 LIMIT 3
OFFSET 0;

 QUERY PLAN

----------------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=12946.83..12946.83 rows=3 width=1175) (actual
time=0.123..0.131 rows=1 loops=1)
   ->  Sort  (cost=12946.83..12950.83 rows=1602 width=1175) (actual
time=0.116..0.119 rows=1 loops=1)
         Sort Key: foos.attr1
         ->  Nested Loop  (cost=28.69..12035.56 rows=1602 width=1175)
(actual time=0.071..0.086 rows=1 loops=1)
               ->  Bitmap Heap Scan on bars  (cost=28.69..2059.66
rows=1602 width=4) (actual time=0.036..0.039 rows=1 loops=1)
                     Recheck Cond: (bars_id = 12345)
                     ->  Bitmap Index Scan on index_bars_on_bars_id
(cost=0.00..28.29 rows=1602 width=0) (actual time=0.024..0.024 rows=1
loops=1)
                           Index Cond: (bars_id = 12345)
               ->  Index Scan using foos_pkey on foos (cost=0.00..6.21
rows=1 width=1175) (actual time=0.017..0.021 rows=1 loops=1)
                     Index Cond: (foos.id = bars.foos_id)
 Total runtime: 0.350 ms

This query is run on a production system and is using foos_1attr1
which is an index on attr1 which is a string.

EXPLAIN ANALYZE SELECT foos.* FROM foos INNER JOIN bars ON foos.id =
bars.foos_id WHERE ((bars.bars_id = 12345)) ORDER BY attr1 LIMIT 3
OFFSET 0;
                                                                    QUERY PLAN

---------------------------------------------------------------------------------------------------------------------------------------------------
 Limit  (cost=0.00..2847.31 rows=3 width=332) (actual
time=6175.515..6414.599 rows=1 loops=1)
   ->  Nested Loop  (cost=0.00..287578.30 rows=303 width=332) (actual
time=6175.510..6414.591 rows=1 loops=1)
         ->  Index Scan using foos_1attr1 on foos
(cost=0.00..128038.65 rows=1602 width=332) (actual
time=0.182..2451.923 rows=2498 loops=1)
         ->  Index Scan using bars_1ix on bars  (cost=0.00..0.37
rows=1 width=4) (actual time=0.006..0.006 rows=0 loops=421939)
               Index Cond: (foos.id = bars.foos_id)
               Filter: (bars_id = 12345)
 Total runtime: 6414.804 ms