The phrase "tossed it in" can be replaced with antonyms that convey a sense of care, thoughtfulness, and intentionality. Instead of hastily getting rid of something, you can choose to deposit it, place it, or carefully position it. If you want to express the idea of keeping something safe and secure, consider words like store, hide, safeguard, or preserve. These antonyms offer a more deliberate and attentive approach to handling objects, giving them value and worth beyond mere disposability. By choosing careful antonyms for "tossed it in," you can highlight the importance of treating belongings and possessions with care and respect.