That's a great and practical question! It really depends on the specific design and quality of the bin. In most public spaces and for better-quality home bins, the lids are *permanently attached* via durable hinges or a central pivot point. You can lift them open, but they won't detach completely under normal use, preventing loss. Common attachment methods include sturdy metal or plastic hinge pins, integrated plastic living hinges, or a central rod that the lid clips onto.
However, on some cheaper or older models, especially lightweight plastic bins, the lid might simply sit in a groove or rest loosely on top. These can indeed blow off in strong wind or be knocked off easily, potentially getting lost. When purchasing, look for terms like "attached lid," "hinged lid," or "secured lid." Features like locking tabs or a handle that clips under the rim also indicate a more secure, loss-resistant design. So, while the standard is for lids to be attached, it's not universal—checking the mechanism is always wise.