This only happens for a few items and is not something that is easily reproduced in my experience.

While the expected behavior would be the item to be temporary blacklisted for the entire session, sometimes it resets right away and immediately places the item back in the button with the following messages outputed into chat:

[01:52:23] [NOP] Temporary Blacklisted: A Guide to Rare Fish 
[01:52:24] [NOP] Temporary blacklist cleared, restarting lookup

Using verbose mode for the latest occurrance I got the following:

[01:46:36] [NOP] Temporary Blacklisted: A Guide to Rare Fish
[01:46:36] [NOP] ItemIsBlacklisted: itemID 199061 is temporary blacklisted
[01:46:36] [NOP] ItemScan: itemID 199061 is blacklisted
[01:46:36] [NOP] ItemShowNew: itemID 198131 Zone yes Priority 2 Stamp 148901.352
[01:46:36] [NOP] itemID 198131 has red text in tooltip! Requires Dragon Isles Cooking (40)
[01:46:36] [NOP] ItemShowNew: itemID 194963 Zone yes Priority 2 Stamp 148901.353
[01:46:36] [NOP] itemID 194963 has red text in tooltip! Requires Dragon Isles Blacksmithing (50)
[01:46:36] [NOP] ItemShowNew: itemID 201785 Zone yes Priority 2 Stamp 148901.355
[01:46:36] [NOP] itemID 201785 has red text in tooltip! Requires Dragon Isles Cooking (30)
[01:46:36] [NOP] Temporary blacklist cleared, restarting lookup!
[01:46:37] [NOP] ItemGetSpell: itemID 198131 spell Learning
[01:46:37] [NOP] ItemIsBlacklisted: itemID 128314 is permanently blacklisted
[01:46:37] [NOP] ItemScan: itemID 128314 is blacklisted
[01:46:37] [NOP] ItemGetSpell: itemID 194963 spell Learning
[01:46:37] [NOP] ItemGetSpell: itemID 201785 spell Learning
[01:46:37] [NOP] ItemShowNew: itemID 199061 Zone yes Priority 2 Stamp 148993.82
[01:46:37] [NOP] ItemShowNew: itemID 201785 Zone yes Priority 2 Stamp 148901.355
[01:46:37] [NOP] itemID 201785 has red text in tooltip! Requires Dragon Isles Cooking (30)
[01:46:37] [NOP] ItemShowNew: itemID 194963 Zone yes Priority 2 Stamp 148901.353
[01:46:37] [NOP] itemID 194963 has red text in tooltip! Requires Dragon Isles Blacksmithing (50)
[01:46:37] [NOP] ItemShowNew: itemID 198131 Zone yes Priority 2 Stamp 148901.352
[01:46:37] [NOP] itemID 198131 has red text in tooltip! Requires Dragon Isles Cooking (40)
[01:46:37] [NOP] ButtonShow: macro text /use item:199061
[01:46:39] [NOP] ItemGetSpell: itemID 198131 spell Learning
[01:46:39] [NOP] ItemIsBlacklisted: itemID 128314 is permanently blacklisted
[01:46:39] [NOP] ItemScan: itemID 128314 is blacklisted
[01:46:39] [NOP] ItemGetSpell: itemID 194963 spell Learning
[01:46:39] [NOP] ItemGetSpell: itemID 201785 spell Learning
[01:46:39] [NOP] ItemShowNew: itemID 199061 Zone yes Priority 2 Stamp 148993.82
[01:46:39] [NOP] ItemShowNew: itemID 198131 Zone yes Priority 2 Stamp 148901.352
[01:46:39] [NOP] itemID 198131 has red text in tooltip! Requires Dragon Isles Cooking (40)
[01:46:39] [NOP] ItemShowNew: itemID 194963 Zone yes Priority 2 Stamp 148901.353
[01:46:39] [NOP] itemID 194963 has red text in tooltip! Requires Dragon Isles Blacksmithing (50)
[01:46:39] [NOP] ItemShowNew: itemID 201785 Zone yes Priority 2 Stamp 148901.355
[01:46:39] [NOP] itemID 201785 has red text in tooltip! Requires Dragon Isles Cooking (30)
[01:46:42] [NOP] ItemShowNew: itemID 199061 Zone yes Priority 2 Stamp 148993.82
[01:46:42] [NOP] ItemShowNew: itemID 198131 Zone yes Priority 2 Stamp 148901.352
[01:46:42] [NOP] itemID 198131 has red text in tooltip! Requires Dragon Isles Cooking (40)
[01:46:42] [NOP] ItemShowNew: itemID 194963 Zone yes Priority 2 Stamp 148901.353
[01:46:42] [NOP] itemID 194963 has red text in tooltip! Requires Dragon Isles Blacksmithing (50)
[01:46:42] [NOP] ItemShowNew: itemID 201785 Zone yes Priority 2 Stamp 148901.355
[01:46:42] [NOP] itemID 201785 has red text in tooltip! Requires Dragon Isles Cooking (30)

That is most likely due to the "Session skip" option being disabled. Try enabling this to keep items blacklisted until re-logging.

While I believed I had this marked it was not the case, I am sorry for wasting your time.

No time wasted. Thank you for confirming.