Place scanners before hay is sold or burned

Trace every path out of the hay pile

1. Start at each pickup route. Follow the hay from the pile through the belts or arms you actually use.
2. Place scanning before the risky destination. In the source discussion, players recommend scanning before the furnace/generators and before selling. Scanning loose hay early avoids relying on claims about scanning finished products.
3. Check branches and shortcuts. If a branch goes around the scanner to a furnace or sell stand, that hay has not been covered by the scanning route. Faster bypasses change what you are inspecting.
4. Compare scanner coverage with incoming hay. The replies suggest several scanners when one is insufficient, but provide no measured ratio. Check the actual flow and bottleneck in your factory before buying more.

Routing advice is based on player replies, not a measured guarantee that a scanner catches every needle at every speed.

Check arms that bypass the scanning route

In EvilGreebo's October 6 paper-mill discussion, PuzzleheadedBasil384 noticed that the top arms were not being scanned; the factory owner acknowledged the missed branch. Trace arm-fed output as well as belts before expanding the factory.

If hay reaches the scanner but it is not operating, inspect the actual power connection and machine indicator. In a separate September 28 question, a reply asked about power and reported four scanners working in that player's setup. There was no confirmed fix for the original poster, and neither discussion identifies a build. Four scanners is not a prescribed ratio.

Loose hay, bales and finished products

lieutenantkirtar cites a tooltip that loose hay scans quickest. dontnormally says scanners work on hay and bales, while a later reply says hay-bale scanning needs an upgrade. Check your scanner's current tooltip and upgrades before feeding bales.

KITOMER reports scanners pulling needles from finished products, including paper rolls; another player disputes the paper claim. That disagreement is why this guide uses scanning before processing as its starting route. It does not promise that every finished product can be scanned.

If you have a suspicious bale or brick

In the October 6 “Selling before scanning” thread, GameOverRIP reports a tooltip saying you can look at a bale or brick and use X to tear it apart and retrieve a needle. If your build displays that instruction, follow the prompt before sending the item to SELL.

This is a pre-sale action reported from a tooltip, not a method to recover an already sold object. The post names no build and supplies no screenshot. If X has a different action in your build, follow the game prompt rather than this historical key report.

Already sold a needle?

The reports conflict. Some October 5–6 replies say sold needles return to the pile; sawras reports the SELL point consuming one, and the later tooltip report warns of loss. Do not treat either return-to-pile or permanent loss as established for every build.

No reliable sold-needle detector, save-file recovery or rollback procedure was established by these sources. sawras also says Alt+F4 apparently saved and quit, so force-closing is not a reliable undo technique.

Record your build, what was sold and the route it took. Use the sale discussion for current follow-up. Do not edit your only save using an invented file path or recovery promise.

A quiet scanner is not proof of a lost needle

The original question followed five hours without a find. Another player, Lapio, later reported finding the sixth needle with 13 million hay left after being worried at 137 million. That is one playthrough, not a schedule you can expect.

First check that the hay reaches the scanner. A long wait, remaining-hay count or silent scanner does not by itself show that you sold a needle or that a save is broken.